configure.ac: Substitute GOC_FOR_TARGET and GCC_FOR_TARGET.
* configure.ac: Substitute GOC_FOR_TARGET and GCC_FOR_TARGET.
* Makefile.am (MOSTLYCLEANFILES): Add check-gcc.
(check-gccgo): Create via a temporary file.
(check-gcc): New target.
(CHECK_ENV): Set CC.
(ECHO_ENV): Report CC.
(check-go-tool): Depend on check-gcc.
(check-runtime, check-cgo-test, check-carchive-test): Likewise.
* configure, Makefile.in: Rebuild.