Mark ARM asm objects as allowing a non-executable stack.

This adds the magic .note.GNU-stack section at the end of each ARM
 asm file (when built with gas), indicating that a non-executable
 stack is allowed.
Without this section, the linker will assume the object requires an
 executable stack by default, forcing an executable stack for the
 entire program.

Change-Id: Ie86de6a449b52d392b9e5e0479833ed8c508ee65

build/make/ads2gas.pl

@@ -154,3 +154,6 @@ while (<STDIN>)
     next if /^\s*END\s*$/;
     print;
 }
+
+# Mark that this object doesn't need an executable stack.
+printf ("\t.section\t.note.GNU-stack,\"\",\%\%progbits\n");