Split up source and added basic support for different targets.

SConstruct

@@ -1,52 +1,36 @@
 
 import subprocess
 
+AddOption(
+    '--target',
+    dest = 'target',
+    type = 'choice',
+    choices = ('i686', 'x86_64'),
+    nargs = 1,
+    action = 'store',
+    default = 'i686'
+)
+
+target  = GetOption('target')
+
 env = Environment(tools =  ['default', 'compilation_db'])
-env['AS'] = 'i686-elf-as'
-env['CC'] = 'i686-elf-gcc'
-env['CXX'] = 'i686-elf-g++'
-env['LD'] = 'i686-elf-g++'
 env.Append(CXXFLAGS = ['-ffreestanding', '-fno-exceptions', '-fno-rtti', '-std=c++20'])
 env.Append(LINKFLAGS = ['-T', 'linker.ld', '-ffreestanding', '-nostdlib'])
-env.Append(CPPPATH = ['#include', '#bastl/include'])
+env.Append(CPPPATH = ['#targets/_any/include', '#bastl/include'])
 env.Append(CCFLAGS = ['-g', '-O0'])
 
-def get_crt_object(name: str) -> str:
-    cmd = [env['CXX']]
-    cmd.extend(env['CXXFLAGS'])
-    cmd.append(f'-print-file-name={name}')
-    result = subprocess.run(cmd, stdout=subprocess.PIPE)
-    return result.stdout.decode('utf-8').strip()
-crtbegin_o = get_crt_object('crtbegin.o')
-crtend_o = get_crt_object('crtend.o')
-crti_o = env.Object('src/crt/crti.s')
-crtn_o = env.Object('src/crt/crtn.s')
-
-os_sources = Split('''
-    src/app/main.cpp
-
-    src/kernel/boot.s
-    src/kernel/startup.cpp
-
-    src/os/panic.cpp
-    src/os/tty.cpp
-
-    src/cstdlib/assert.cpp
-    src/cstdlib/stdio.cpp
-    src/cstdlib/stdlib.cpp
-    src/cstdlib/string.cpp
-
-    bastl/src/exception.cpp
-    bastl/src/new.cpp
-''')
-env['LINKCOM'] = env['LINKCOM'].replace('$_LIBFLAGS', f'{crti_o[0]} {crtbegin_o} $_LIBFLAGS {crtend_o} {crtn_o[0]}')
+env['KERNEL_SOURCES'] = []
+env['KERNEL_DEPENDENCIES'] = []
+env = SConscript('bastl/SConscript', exports = 'env')
+env = SConscript('targets/_any/SConscript', exports = 'env')
+env = SConscript(f'targets/{target}/SConscript', exports = 'env')
 
 prog_os = env.Program(
     target = 'os.bin',
-    source = os_sources,
+    source = env['KERNEL_SOURCES'],
     LIBS = ['gcc']
 )
-env.Depends(prog_os, [crti_o, crtn_o])
+env.Depends(prog_os, env['KERNEL_DEPENDENCIES'])
 env.Default(prog_os)
 comp_db = env.CompilationDatabase(target = '#compile_commands.json')
 env.Default(comp_db)