gcc: improve spec file
gcc: improve spec file

The current spec file adds:
/home/linuxbrew/.linuxbrew/lib/gcc/11
/home/linuxbrew/.linuxbrew/lib

in front of the rpath.
In the case $ORIGIN was used, this might be an issue.
For example openjdk relies on $ORIGIN to find libnet.so,
so putting our libnet.so in front of $ORIGIN breaks
openjdk at runtime.

This pull reauests moves #{HOMEBREW_PREFIX}/lib away from
the *link stanza. We do want to keep gcc 11 in front though,
to make sure gcc libs are always loaded first.

homebrew_rpath is needed to help the compiler find it's libraries.

filcab/homebrew-core,mfikes/homebrew-core,cblecker/homebrew-core,lemzwerg/homebrew-core,filcab/homebrew-core,zyedidia/homebrew-core,stgraber/homebrew-core,uyjulian/homebrew-core,chrisfinazzo/homebrew-core,makigumo/homebrew-core,adam-moss/homebrew-core,nandub/homebrew-core,sjackman/homebrew-core,zyedidia/homebrew-core,nbari/homebrew-core,nbari/homebrew-core,Homebrew/homebrew-core,mfikes/homebrew-core,nandub/homebrew-core,chrisfinazzo/homebrew-core,lemzwerg/homebrew-core,Homebrew/homebrew-core,adam-moss/homebrew-core,makigumo/homebrew-core,uyjulian/homebrew-core,cblecker/homebrew-core,stgraber/homebrew-core,sjackman/homebrew-core