gummiboot: build without -nostdinc

gnu-efi-libs needs stddef.h now.
It should be ok to be included, even if in -ffreestanding,
systemd-boot also dropped -nostdinc.

Close: #49859

srcpkgs/gummiboot/patches/remove-nostdinc.patch

@@ -0,0 +1,14 @@
+--- a/Makefile.am
++++ b/Makefile.am
+@@ -86,11 +86,9 @@ efi_cflags = \
+ 	-Wall \
+ 	-Wextra \
+ 	-std=gnu90 \
+-	-nostdinc \
+ 	-ggdb -O0 \
+ 	-fpic \
+ 	-fshort-wchar \
+-	-nostdinc \
+ 	-ffreestanding \
+ 	-fno-strict-aliasing \
+ 	-fno-stack-protector \

srcpkgs/gummiboot/patches/stub.patch

@@ -1,6 +1,6 @@
---- a/src/efi/stub.c	2015-03-12 00:50:35.000000000 +0100
+--- a/src/efi/stub.c
-+++ b/src/efi/stub.c	2020-07-06 12:32:55.985327487 +0200
++++ b/src/efi/stub.c
-@@ -83,7 +83,7 @@
+@@ -83,7 +83,7 @@ EFI_STATUS efi_main(EFI_HANDLE image, EF
          cmdline_len = szs[0];
  
          /* if we are not in secure boot mode, accept a custom command line and replace the built-in one */
@@ -9,4 +9,3 @@
                  CHAR16 *options;
                  CHAR8 *line;
                  UINTN i;
-