build is missing command line flags to clang-tidy

[vtjnash]

Since c3a08fe, we no longer pass user flags (CFLAGS, etc) to the analysis tools, since these are added directly to JCFLAGS instead of JCFLAGS_common. Additionally, we set some options in FLAGS based on the selected GCC compiler, even though we are passing those to clang. It looks like the logic for combining the FLAGS_* into FLAGS needs to move deeper and later in to the Makefiles