efi/libstub: Use hidden visibility for all source files

Instead of setting the visibility pragma for a small set of symbol
declarations that could result in absolute references that we cannot
support in the stub, declare hidden visibility for all code in the
EFI stub, which is more robust and future proof.

To ensure that the #pragma is taken into account before any other
includes are processed, put it in a header file of its own and
include it via the compiler command line using the -include option.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
diff --git a/drivers/firmware/efi/libstub/arm64-stub.c b/drivers/firmware/efi/libstub/arm64-stub.c
index ad5f24a..9254cd8 100644
--- a/drivers/firmware/efi/libstub/arm64-stub.c
+++ b/drivers/firmware/efi/libstub/arm64-stub.c
@@ -6,17 +6,11 @@
  * Adapted from ARM version by Mark Salter <msalter@redhat.com>
  */
 
-/*
- * To prevent the compiler from emitting GOT-indirected (and thus absolute)
- * references to the section markers, override their visibility as 'hidden'
- */
-#pragma GCC visibility push(hidden)
-#include <asm/sections.h>
-#pragma GCC visibility pop
 
 #include <linux/efi.h>
 #include <asm/efi.h>
 #include <asm/memory.h>
+#include <asm/sections.h>
 #include <asm/sysreg.h>
 
 #include "efistub.h"