[lldb][test] Only add -m(64|32) for GCC on non Arm/AArch64 platforms

This option is definitely needed for x86_64, and is valid for PowerPC
and s390x too.

I'm using "in" because on Armv8 Linux the uname is actually "armv8l"
not just "arm".

Author: DavidSpickett

lldb/test/Shell/helper/build.py

@@ -747,7 +747,10 @@ def _get_compilation_command(self, source, obj):
         args = []
 
         args.append(self.compiler)
-        args.append("-m" + self.arch)
+
+        uname = platform.uname().machine.lower()
+        if not "arm" in uname and not "aarch64" in uname:
+            args.append("-m" + self.arch)
 
         args.append("-g")
         if self.opt == "none":
@@ -784,7 +787,11 @@ def _get_compilation_command(self, source, obj):
     def _get_link_command(self):
         args = []
         args.append(self.compiler)
-        args.append("-m" + self.arch)
+
+        uname = platform.uname().machine.lower()
+        if not "arm" in uname and not "aarch64" in uname:
+            args.append("-m" + self.arch)
+
         if self.nodefaultlib:
             args.append("-nostdlib")
             args.append("-static")