* restrict use of LLVM for Gallium to platforms with LLVM in base to fix
runtime errors when Gallium is built with a mix of GCC and LLVM
* make LLVM only a BUILD_DEPEND for mesa-libs, which needs it to build EGL
* add pkg-plist entries for freedreno and vc4 drivers [1]
* remove extraneous SHEBANG_FILES entry to fix build of freedreno [2,3]
* correct typo in libosmesa, which may have affected the Gallium build [4]
PR: 219247 [1], 219406 [3]
Submitted by: jbeich [1] (2 patches, pkg-plist fix), strejda (vc4 CFLAGS)
Reported by: strejda [2], andrew [3], linimon [4]
Approved by: swills (mentor)
Differential Revision: https://reviews.freebsd.org/D10842
943c52c8cc