[openwrt/openwrt] toolchain/gdb: fix broken configure test for ELF support

[LEDE Commits]

nbd pushed a commit to openwrt/openwrt.git, branch master:
https://git.openwrt.org/3f4b382c3cbcb9ae3e2ecce781a766af927d2791

commit 3f4b382c3cbcb9ae3e2ecce781a766af927d2791
Author: Felix Fietkau <nbd at nbd.name>
AuthorDate: Mon May 17 17:16:56 2021 +0200

    toolchain/gdb: fix broken configure test for ELF support
    
    A missing #include was causing gdb on macOS to be compiled without ELF support
    
    Signed-off-by: Felix Fietkau <nbd at nbd.name>
---
 .../gdb/patches/100-fix-elf-support-check.patch      | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/toolchain/gdb/patches/100-fix-elf-support-check.patch b/toolchain/gdb/patches/100-fix-elf-support-check.patch
new file mode 100644
index 0000000000..fe612c38db
--- /dev/null
+++ b/toolchain/gdb/patches/100-fix-elf-support-check.patch
@@ -0,0 +1,20 @@
+--- a/gdb/configure
++++ b/gdb/configure
+@@ -16818,6 +16818,7 @@ else
+   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+ /* end confdefs.h.  */
+ #include <stdlib.h>
++#include <string.h>
+   #include "bfd.h"
+   #include "elf-bfd.h"
+ 
+--- a/gdb/acinclude.m4
++++ b/gdb/acinclude.m4
+@@ -362,6 +362,7 @@ AC_DEFUN([GDB_AC_CHECK_BFD], [
+   AC_CACHE_CHECK([$1], [$2],
+   [AC_TRY_LINK(
+   [#include <stdlib.h>
++  #include <string.h>
+   #include "bfd.h"
+   #include "$4"
+   ],