macOS: use GCC 10 for building, since GCC 9 is no longer in Homebrew

(manually cherry picked from commit 7738ea0a)

macOS/build.sh

@@ -22,8 +22,8 @@ set -ex
 ROOTDIR=$(pwd)/..
 
 # Set the compilers
-CC=gcc-9
-CXX=g++-9
+CC=gcc-10
+CXX=g++-10
 
 # Set the number of threads
 NTHREADS=$(nproc)

preprocessor @ 553c2633

-Subproject commit d39fca02b477e289d5cf95fd7693c64fb4524f66
+Subproject commit 553c26337d457dfcedee2c4fce0bbfb8ed349f6b