Utilities/Release: Drop Linux .tar.Z binary

On Linux the gzip tool is universally available, so our `.tar.gz` is
sufficient.

Utilities/Release/linux64_release.cmake

@@ -2,6 +2,7 @@ set(PROCESSORS 4)
 set(BOOTSTRAP_ARGS "--docdir=doc/cmake")
 set(HOST linux64)
 set(MAKE_PROGRAM "make")
+set(CPACK_BINARY_GENERATORS "STGZ TGZ")
 set(CC /opt/gcc-6.1.0/bin/gcc)
 set(CXX /opt/gcc-6.1.0/bin/g++)
 set(CFLAGS   "")