diff --git a/ci/ci_autotools.sh b/ci/ci_autotools.sh
index 6f4dc1305..4b4d04b87 100755
--- a/ci/ci_autotools.sh
+++ b/ci/ci_autotools.sh
@@ -4,12 +4,13 @@ set -e
 # ci_autotools.sh
 # Continuously integrate libpng using the GNU Autotools.
 #
-# Copyright (c) 2019-2020 Cosmin Truta.
+# Copyright (c) 2019-2021 Cosmin Truta.
 #
 # This software is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
 # and license in png.h.
 
+readonly CI_SYSNAME="$(uname -s)"
 readonly CI_SCRIPTNAME="$(basename "$0")"
 readonly CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
 readonly CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
@@ -35,8 +36,10 @@ function ci_spawn {
 function ci_init_autotools {
     # Initialize the CI_ variables with default values, where applicable.
     CI_MAKE="${CI_MAKE:-make}"
-    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    [[ $CI_SYSNAME == Darwin || $CI_SYSNAME == *BSD || $CI_SYSNAME == DragonFly ]] &&
+        CI_CC="${CI_CC:-clang}"
     # Print the CI_ variables.
+    ci_info "system name: $CI_SYSNAME"
     ci_info "source directory: $CI_SRCDIR"
     ci_info "build directory: $CI_BUILDDIR"
     ci_info "install directory: $CI_INSTALLDIR"
diff --git a/ci/ci_cmake.sh b/ci/ci_cmake.sh
index 37792b4b5..cbee18083 100755
--- a/ci/ci_cmake.sh
+++ b/ci/ci_cmake.sh
@@ -4,19 +4,18 @@ set -e
 # ci_cmake.sh
 # Continuously integrate libpng using CMake.
 #
-# Copyright (c) 2019-2020 Cosmin Truta.
+# Copyright (c) 2019-2021 Cosmin Truta.
 #
 # This software is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
 # and license in png.h.
 
+readonly CI_SYSNAME="$(uname -s)"
 readonly CI_SCRIPTNAME="$(basename "$0")"
 readonly CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
 readonly CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
 readonly CI_BUILDDIR="$CI_SRCDIR/out/cmake.build"
 readonly CI_INSTALLDIR="$CI_SRCDIR/out/cmake.install"
-readonly CI_SRCDIR_REL_BUILDDIR="../.."
-readonly CI_INSTALLDIR_REL_BUILDDIR="../../out/cmake.install"
 
 function ci_info {
     printf >&2 "%s: %s\\n" "$CI_SCRIPTNAME" "$*"
@@ -38,12 +37,34 @@ function ci_init_cmake {
     # Initialize the CI_ variables with default values, where applicable.
     CI_CMAKE="${CI_CMAKE:-cmake}"
     CI_CTEST="${CI_CTEST:-ctest}"
-    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    [[ $CI_SYSNAME == Darwin || $CI_SYSNAME == *BSD || $CI_SYSNAME == DragonFly ]] &&
+        CI_CC="${CI_CC:-clang}"
     CI_CMAKE_BUILD_TYPE="${CI_CMAKE_BUILD_TYPE:-Release}"
+    [[ $CI_CMAKE_GENERATOR == "Visual Studio"* ]] && {
+        # Initialize the CI_..._NATIVE variables.
+        if [[ -x $CYGPATH ]]
+        then
+            CI_SRCDIR_NATIVE="$("$CYGPATH" -w "$CI_SRCDIR")"
+            CI_BUILDDIR_NATIVE="$("$CYGPATH" -w "$CI_BUILDDIR")"
+            CI_INSTALLDIR_NATIVE="$("$CYGPATH" -w "$CI_INSTALLDIR")"
+        else
+            CI_SRCDIR_NATIVE="$(cd "$CI_SRCDIR" ; pwd -W || pwd -P)"
+            CI_BUILDDIR_NATIVE="$(cd "$CI_BUILDDIR" ; pwd -W || pwd -P)"
+            CI_INSTALLDIR_NATIVE="$(cd "$CI_INSTALLDIR" ; pwd -W || pwd -P)"
+        fi
+        # Clean up incidental mixtures of Windows and Bash-on-Windows
+        # environment variables, to avoid confusing MSBuild.
+        [[ $TEMP && ( $Temp || $temp ) ]] && unset TEMP
+        [[ $TMP && ( $Tmp || $tmp ) ]] && unset TMP
+    }
     # Print the CI_ variables.
+    ci_info "system name: $CI_SYSNAME"
     ci_info "source directory: $CI_SRCDIR"
+    [[ $CI_SRCDIR_NATIVE ]] && ci_info "source directory (native): $CI_SRCDIR_NATIVE"
     ci_info "build directory: $CI_BUILDDIR"
+    [[ $CI_BUILDDIR_NATIVE ]] && ci_info "build directory (native): $CI_BUILDDIR_NATIVE"
     ci_info "install directory: $CI_INSTALLDIR"
+    [[ $CI_INSTALLDIR_NATIVE ]] && ci_info "install directory (native): $CI_INSTALLDIR_NATIVE"
     ci_info "environment option: \$CI_CMAKE='$CI_CMAKE'"
     ci_info "environment option: \$CI_CMAKE_GENERATOR='$CI_CMAKE_GENERATOR'"
     ci_info "environment option: \$CI_CMAKE_GENERATOR_PLATFORM='$CI_CMAKE_GENERATOR_PLATFORM'"
@@ -81,25 +102,21 @@ function ci_build_cmake {
     ALL_CMAKE_VARS+=($CI_CMAKE_VARS)
     local -a ALL_CMAKE_BUILD_FLAGS=($CI_CMAKE_BUILD_FLAGS)
     local -a ALL_CTEST_FLAGS=($CI_CTEST_FLAGS)
+    # Initialize SRCDIR_NATIVE and INSTALLDIR_NATIVE.
+    local SRCDIR_NATIVE="${CI_SRCDIR_NATIVE:-"$CI_SRCDIR"}"
+    local INSTALLDIR_NATIVE="${CI_INSTALLDIR_NATIVE:-"$CI_INSTALLDIR"}"
     # Export the CMake build environment.
     [[ $CI_CMAKE_GENERATOR ]] &&
         ci_spawn export CMAKE_GENERATOR="$CI_CMAKE_GENERATOR"
     [[ $CI_CMAKE_GENERATOR_PLATFORM ]] &&
         ci_spawn export CMAKE_GENERATOR_PLATFORM="$CI_CMAKE_GENERATOR_PLATFORM"
-    # Fix the build environment, if necessary.
-    [[ $CI_CMAKE_GENERATOR == "Visual Studio "* ]] && {
-        # Clean up incidental mixtures of Windows and Bash-on-Windows
-        # environment variables, to avoid confusing MSBuild.
-        [[ $TEMP && ( $Temp || $temp ) ]] && unset TEMP
-        [[ $TMP && ( $Tmp || $tmp ) ]] && unset TMP
-    }
     # Build and install.
     ci_spawn rm -fr "$CI_BUILDDIR" "$CI_INSTALLDIR"
     ci_spawn mkdir -p "$CI_BUILDDIR"
     ci_spawn cd "$CI_BUILDDIR"
     ci_spawn "$CI_CMAKE" "${ALL_CMAKE_VARS[@]}" \
-                         -DCMAKE_INSTALL_PREFIX="$CI_INSTALLDIR_REL_BUILDDIR" \
-                         "$CI_SRCDIR_REL_BUILDDIR"
+                         -DCMAKE_INSTALL_PREFIX="$INSTALLDIR_NATIVE" \
+                         "$SRCDIR_NATIVE"
     ci_spawn "$CI_CMAKE" --build . \
                          --config "$CI_CMAKE_BUILD_TYPE" \
                          "${ALL_CMAKE_BUILD_FLAGS[@]}"
diff --git a/ci/ci_legacy.sh b/ci/ci_legacy.sh
index 58a8005ea..d373adeb7 100755
--- a/ci/ci_legacy.sh
+++ b/ci/ci_legacy.sh
@@ -4,12 +4,13 @@ set -e
 # ci_legacy.sh
 # Continuously integrate libpng using the legacy makefiles.
 #
-# Copyright (c) 2019-2020 Cosmin Truta.
+# Copyright (c) 2019-2021 Cosmin Truta.
 #
 # This software is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
 # and license in png.h.
 
+readonly CI_SYSNAME="$(uname -s)"
 readonly CI_SCRIPTNAME="$(basename "$0")"
 readonly CI_SCRIPTDIR="$(cd "$(dirname "$0")" && pwd)"
 readonly CI_SRCDIR="$(dirname "$CI_SCRIPTDIR")"
@@ -34,13 +35,15 @@ function ci_spawn {
 function ci_init_legacy {
     # Initialize the CI_ variables with default values, where applicable.
     CI_MAKE="${CI_MAKE:-make}"
-    [[ $(uname -s || echo unknown) == Darwin ]] && CI_CC="${CI_CC:-clang}"
+    [[ $CI_SYSNAME == Darwin || $CI_SYSNAME == *BSD || $CI_SYSNAME == DragonFly ]] &&
+        CI_CC="${CI_CC:-clang}"
     [[ $CI_CC == *clang* ]] &&
-        CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-scripts/makefile.clang}"
-    CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-scripts/makefile.gcc}"
-    CI_LD="${CI_LD:-$CI_CC}"
-    CI_LIBS="${CI_LIBS:--lz -lm}"
+        CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-"scripts/makefile.clang"}"
+    CI_LEGACY_MAKEFILES="${CI_LEGACY_MAKEFILES:-"scripts/makefile.gcc"}"
+    CI_LD="${CI_LD:-"$CI_CC"}"
+    CI_LIBS="${CI_LIBS:-"-lz -lm"}"
     # Print the CI_ variables.
+    ci_info "system name: $CI_SYSNAME"
     ci_info "source directory: $CI_SRCDIR"
     ci_info "build directory: $CI_BUILDDIR"
     ci_info "environment option: \$CI_LEGACY_MAKEFILES='$CI_LEGACY_MAKEFILES'"