* tests/subobj3.test: Exit with status 77 if gcc not found.
* tests/pr9.test: Exit with status 77 if gzip not found.
* tests/pr87.test: Exit with status 77 if gcc not found.
* tests/pr19.test: Exit with status 77 if gzip or gcc not found.
* tests/install2.test: Exit with status 77 if gzip not found.
* tests/exsource.test: Exit with status 77 if GNU make not found.
* tests/ansi3.test: Exit with status 77 if gcc not found.
* tests/target-cflags.test: Require GNU make. Exit with status 77
if gcc or make not found. Fixes PR automake/121.