Split local and global cflags

Native compiler flags are currently applied in approximately:
global cflags
local cflags
local include dirs
global include dirs
global conlyflags
local conlyflags
global cppflags
local cppflags

This means that a flag that is enabled in the global cppflags
cannot be disabled in the local cflags, and an Android.bp author
must know to disable it in the local cppflags.  A better order
would be:
global cflags
global conlyflags
global cppflags
local cflags
local conlyflags
local cppflags
local include dirs
global include dirs

We are mixing both the global and local cflags into a single
variable, and similar for conlyflags and cppflags, which
prevents reordering them.  This CL prepares to reorder them
by splitting the global and local cflags into separate variables.

Bug: 143713277
Test: m native
Change-Id: Ic55a8c3516c331dc5f2af9d00e59ceca9d3e6c15
diff --git a/cc/xom.go b/cc/xom.go
index 9337990..e1cac53 100644
--- a/cc/xom.go
+++ b/cc/xom.go
@@ -68,7 +68,7 @@
 	if !disableXom || (xom.Properties.Xom != nil && *xom.Properties.Xom) {
 		// XOM is only supported on AArch64 when using lld.
 		if ctx.Arch().ArchType == android.Arm64 && ctx.useClangLld(ctx) {
-			flags.LdFlags = append(flags.LdFlags, "-Wl,-execute-only")
+			flags.Local.LdFlags = append(flags.Local.LdFlags, "-Wl,-execute-only")
 		}
 	}