gn_base.bbclass: Refine build directory check

To keep GN happy not only the build directory cannot be the same as sources, but also build directory has to be a sub-directory of the sources. This is caused by the fact that GN handles references as relative to the source directory being the root directory. Therefore it is impossible to reference locations outside the GN root directory tree.

meta-oniro-staging/classes/gn_base.bbclass

@@ -52,7 +52,7 @@ EXPORT_FUNCTIONS do_configure do_compile do_install
 python do_check_B_is_not_S() {
     bpath = os.path.abspath(d.expand("${B}"))
     spath = os.path.abspath(d.expand("${S}"))
-    if os.path.abspath(d.expand("${S}")) == os.path.abspath(d.expand("${B}")):
+    if os.path.samefile(bpath, spath):
         bb.fatal('''
 GN requires build and sources directories to be different. By default build
 directory is set to ${WORKDIR}/out. If you're using devtool remember to use
@@ -82,7 +82,7 @@ def gn_target_arch_name(d):
     """Returns a GN architecture name corresponding to the target machine's
     architecture."""
     name = d.getVar("GN_TARGET_ARCH_NAME")
-    if name is None:
+    if not name:
         bb.fatal('Unsupported target architecture. A valid override for the '
                  'GN_TARGET_ARCH_NAME variable could not be found.')
     return name