Revert "Toolchains: Update to GCC 10.5.0"

I pushed the wrong working tree AGAIN

This reverts commit b92033f716.

tools/toolchain-patches/apple_silicon-zlib.patch

@@ -1,14 +1,14 @@
 diff --git a/zlib/zutil.h b/zlib/zutil.h
-index 4b596adf..66d54cc3 100644
+index ed6b127e..3186e991 100644
 --- a/zlib/zutil.h
 +++ b/zlib/zutil.h
-@@ -130,17 +130,8 @@ extern z_const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
+@@ -118,17 +118,8 @@ extern const char * const z_errmsg[10]; /* indexed by 2-zlib_error */
  #  endif
  #endif
  
 -#if defined(MACOS) || defined(TARGET_OS_MAC)
 +#if defined(MACOS)
- #  define OS_CODE  7
+ #  define OS_CODE  0x07
 -#  ifndef Z_SOLO
 -#    if defined(__MWERKS__) && __dest_os != __be_os && __dest_os != __win32_os
 -#      include <unix.h> /* for fdopen */
@@ -20,4 +20,4 @@ index 4b596adf..66d54cc3 100644
 -#  endif
  #endif
  
- #ifdef __acorn
+ #ifdef TOPS20