simplify LLVM version string printing

Figure it out once in the build system, then just use that all over the place.

Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

meson.build

@@ -1234,17 +1234,9 @@ if _llvm != 'false'
 endif
 if with_llvm
   _llvm_version = dep_llvm.version().split('.')
-
-  # 3 digits versions in LLVM only started from 3.4.1 on
-  if dep_llvm.version().version_compare('>= 3.4.1')
-    _llvm_patch = _llvm_version[2]
-  else
-    _llvm_patch = '0'
-  endif
-
   pre_args += [
     '-DHAVE_LLVM=0x0@0@0@1@'.format(_llvm_version[0], _llvm_version[1]),
-    '-DMESA_LLVM_VERSION_PATCH=@0@'.format(_llvm_patch),
+    '-DMESA_LLVM_VERSION_STRING="@0@"'.format(dep_llvm.version()),
   ]
 
   # LLVM can be built without rtti, turning off rtti changes the ABI of C++