Remove warnings about mismatched types with builtins for stubs.

Looks like new versions of the toolchain have an error about mismatching
the definitions used in the stubs with the builtin definitions. Since we
don't care about this when building stubs, ignore it by disabling the
builtin definitions.

Bug: N/A
Test: Build platform with ToT LLVM compiler.
Change-Id: I4e449c5fb96d0d5442fd57a7fea02ba69463324b

cc/ndk_library.go

@@ -284,6 +284,10 @@ func parseNativeAbiDefinition(ctx ModuleContext, symbolFile string,
 }
 
 func compileStubLibrary(ctx ModuleContext, flags Flags, src android.Path) Objects {
+	// libc/libm stubs libraries end up mismatching with clang's internal definition of these
+	// functions (which have noreturn attributes and other things). Because we just want to create a
+	// stub with symbol definitions, and types aren't important in C, ignore the mismatch.
+	flags.Local.ConlyFlags = append(flags.Local.ConlyFlags, "-fno-builtin")
 	return compileObjs(ctx, flagsToBuilderFlags(flags), "",
 		android.Paths{src}, nil, nil, nil, nil)
 }