[libc][musl] support arm-linux-musleabi toolchain

目前基本功能已经可以在QEMU上跑起来，但是pthread和内核signal选中会报冲突。先合并一版本，后续解决这些问题。

components/libc/compilers/newlib/SConscript

@@ -3,28 +3,27 @@ from building import *
 from gcc import *
 Import('rtconfig')
 
-src = []
-cwd = GetCurrentDir()
 group = []
-LIBS = []
-CPPPATH = [cwd]
 
-if rtconfig.PLATFORM in ['gcc']:
-    LIBS += ['c', 'm'] # link libc and libm
-    src += Glob('*.c')
+libc_name, libc_version = GetGCCLibcNameVersion(rtconfig)
 
-    #report newlib version
-    print('Newlib version:' + GetNewLibVersion(rtconfig))
+if libc_name == 'newlib':
+    print('Newlib version: ' + libc_version)
 
-    # identify this is Newlib, and only enable POSIX.1-1990
-    CPPDEFINES = ['RT_USING_NEWLIBC', 'RT_USING_LIBC', '_POSIX_C_SOURCE=1']
+    cwd = GetCurrentDir()
+    src = Glob('*.c')
+
+    CPPPATH = [cwd]
+    CPPDEFINES = ['RT_USING_NEWLIBC', 'RT_USING_LIBC', '_POSIX_C_SOURCE=1'] # identify this is Newlib, and only enable POSIX.1-1990
+    LIBS = ['c', 'm'] # link libc and libm
     AddDepend(['RT_USING_NEWLIBC', 'RT_USING_LIBC'])
-    group = DefineGroup('Compiler', src, depend = [''], CPPPATH = CPPPATH, CPPDEFINES = CPPDEFINES, LIBS = LIBS)
 
-list = os.listdir(cwd)
-for d in list:
-    path = os.path.join(cwd, d)
-    if os.path.isfile(os.path.join(path, 'SConscript')):
-        group = group + SConscript(os.path.join(d, 'SConscript'))
+    group = group + DefineGroup('Compiler', src, depend = [''], CPPPATH = CPPPATH, CPPDEFINES = CPPDEFINES, LIBS = LIBS)
+
+    list = os.listdir(cwd)
+    for d in list:
+        path = os.path.join(cwd, d)
+        if os.path.isfile(os.path.join(path, 'SConscript')):
+            group = group + SConscript(os.path.join(d, 'SConscript'))
 
 Return('group')