gcc7: fix build w/glibc-2.31

Applied a patch from the `gcc9` branch for `gcc7` to fix `libsanitizer`
for glibc-2.31.

pkgs/development/compilers/gcc/7/0001-Fix-build-for-glibc-2.31.patch

@@ -0,0 +1,62 @@
+From 2d03b6eaf823fc2db6a32b4a95e18f8a7474b47f Mon Sep 17 00:00:00 2001
+From: Maximilian Bosch <maximilian@mbosch.me>
+Date: Thu, 20 Feb 2020 01:56:42 +0100
+Subject: [PATCH] Fix build for glibc 2.31
+
+---
+ .../sanitizer_platform_limits_posix.cc            |  5 +++--
+ .../sanitizer_platform_limits_posix.h             | 15 +--------------
+ 2 files changed, 4 insertions(+), 16 deletions(-)
+
+diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
+index 97eae3fc7..4089d4695 100644
+--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
++++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.cc
+@@ -1145,8 +1145,9 @@ CHECK_SIZE_AND_OFFSET(ipc_perm, uid);
+ CHECK_SIZE_AND_OFFSET(ipc_perm, gid);
+ CHECK_SIZE_AND_OFFSET(ipc_perm, cuid);
+ CHECK_SIZE_AND_OFFSET(ipc_perm, cgid);
+-#if !defined(__aarch64__) || !SANITIZER_LINUX || __GLIBC_PREREQ (2, 21)
+-/* On aarch64 glibc 2.20 and earlier provided incorrect mode field.  */
++#if !SANITIZER_LINUX || __GLIBC_PREREQ (2, 31)
++/* glibc 2.30 and earlier provided 16-bit mode field instead of 32-bit
++   on many architectures.  */
+ CHECK_SIZE_AND_OFFSET(ipc_perm, mode);
+ #endif
+ 
+diff --git a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
+index c13932283..3456fb2db 100644
+--- a/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
++++ b/libsanitizer/sanitizer_common/sanitizer_platform_limits_posix.h
+@@ -204,27 +204,14 @@ namespace __sanitizer {
+     unsigned __seq;
+     u64 __unused1;
+     u64 __unused2;
+-#elif defined(__mips__) || defined(__aarch64__) || defined(__s390x__)
+-    unsigned int mode;
+-    unsigned short __seq;
+-    unsigned short __pad1;
+-    unsigned long __unused1;
+-    unsigned long __unused2;
+ #elif defined(__sparc__)
+-# if defined(__arch64__)
+     unsigned mode;
+-    unsigned short __pad1;
+-# else
+-    unsigned short __pad1;
+-    unsigned short mode;
+     unsigned short __pad2;
+-# endif
+     unsigned short __seq;
+     unsigned long long __unused1;
+     unsigned long long __unused2;
+ #else
+-    unsigned short mode;
+-    unsigned short __pad1;
++    unsigned int mode;
+     unsigned short __seq;
+     unsigned short __pad2;
+ #if defined(__x86_64__) && !defined(_LP64)
+-- 
+2.25.0
+

pkgs/development/compilers/gcc/7/default.nix

@@ -53,6 +53,8 @@ let majorVersion = "7";
         ./riscv-pthread-reentrant.patch
         # https://gcc.gnu.org/ml/gcc-patches/2018-03/msg00297.html
         ./riscv-no-relax.patch
+
+        ./0001-Fix-build-for-glibc-2.31.patch
       ]
       ++ optional (targetPlatform != hostPlatform) ../libstdc++-target.patch
       ++ optionals targetPlatform.isNetBSD [