Revert "Toolchains: Update to GCC 10.5.0"

I pushed the wrong working tree AGAIN

This reverts commit b92033f716.

tools/toolchain-patches/gcc-libcpp17.patch

@@ -1,66 +0,0 @@
-diff --git a/gcc/system.h b/gcc/system.h
-index d04f8fd33..636084682 100644
---- a/gcc/system.h
-+++ b/gcc/system.h
-@@ -197,25 +197,6 @@ extern int fprintf_unlocked (FILE *, const char *, ...);
- /* Include <string> before "safe-ctype.h" to avoid GCC poisoning
-    the ctype macros through safe-ctype.h */
- 
--#ifdef __cplusplus
--#ifdef INCLUDE_STRING
--# include <string>
--#endif
--#endif
--
--/* There are an extraordinary number of issues with <ctype.h>.
--   The last straw is that it varies with the locale.  Use libiberty's
--   replacement instead.  */
--#include "safe-ctype.h"
--
--#include <sys/types.h>
--
--#include <errno.h>
--
--#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
--extern int errno;
--#endif
--
- #ifdef __cplusplus
- #if defined (INCLUDE_ALGORITHM) || !defined (HAVE_SWAP_IN_UTILITY)
- # include <algorithm>
-@@ -229,6 +210,9 @@ extern int errno;
- #ifdef INCLUDE_SET
- # include <set>
- #endif
-+#ifdef INCLUDE_STRING
-+# include <string>
-+#endif
- #ifdef INCLUDE_VECTOR
- # include <vector>
- #endif
-@@ -237,6 +221,25 @@ extern int errno;
- # include <utility>
- #endif
- 
-+#ifdef __cplusplus
-+#ifdef INCLUDE_STRING
-+# include <string>
-+#endif
-+#endif
-+
-+/* There are an extraordinary number of issues with <ctype.h>.
-+   The last straw is that it varies with the locale.  Use libiberty's
-+   replacement instead.  */
-+#include "safe-ctype.h"
-+
-+#include <sys/types.h>
-+
-+#include <errno.h>
-+
-+#if !defined (errno) && defined (HAVE_DECL_ERRNO) && !HAVE_DECL_ERRNO
-+extern int errno;
-+#endif
-+
- /* Some of glibc's string inlines cause warnings.  Plus we'd rather
-    rely on (and therefore test) GCC's string builtins.  */
- #define __NO_STRING_INLINES