Use CMake option rather than env var

To find non-standard check_clang_tidy.py, was previously using an
environment variable.  Switch to a CMake option instead, so that it's
not necessary to set the env var wherever you run the plugins tests.

CMakeLists.txt

@@ -20,7 +20,8 @@ option(LOCALIZE     "Support for language localizations. Also enable UTF support
 option(LANGUAGES    "Compile localization files for specified languages."			""   )
 option(DYNAMIC_LINKING "Use dynamic linking. Or use static to remove MinGW dependency instead."	"ON")
 option(CATA_CLANG_TIDY_PLUGIN "Build Cata's custom clang-tidy plugin" "OFF")
-set(LLVM_INCLUDE_DIRS "" CACHE STRING "Paths to llvm and clang headers used for clang-tidy plugin")
+set(CATA_CLANG_TIDY_INCLUDE_DIR "" CACHE STRING "Path to internal clang-tidy headers required for plugin (e.g. ClangTidy.h)")
+set(CATA_CHECK_CLANG_TIDY "" CACHE STRING "Path to check_clang_tidy.py for plugin tests")
 set(GIT_BINARY       "" CACHE STRING "Git binary name or path.")
 set(PREFIX           "" CACHE STRING "Location of Data & GFX directories")
 

tools/clang-tidy-plugin/test/lit.cfg

@@ -10,8 +10,9 @@ config.test_exec_root = os.path.join(
 
 config.suffixes = ['.cpp']
 
-check_clang_tidy = os.getenv('CHECK_CLANG_TIDY')
-if not check_clang_tidy:
+if config.cata_check_clang_tidy:
+    check_clang_tidy = config.cata_check_clang_tidy
+else:
     check_clang_tidy = os.path.join(
             config.plugin_build_root, 'clang-tidy-plugin-support', 'bin',
             'check_clang_tidy.py')

tools/clang-tidy-plugin/test/lit.site.cfg.in

@@ -1,6 +1,7 @@
 import os
 
 config.plugin_build_root = "@CMAKE_CURRENT_BINARY_DIR@"
+config.cata_check_clang_tidy = "@CATA_CHECK_CLANG_TIDY@"
 
 lit_config.load_config(
         config, os.path.join("@CMAKE_CURRENT_SOURCE_DIR@", "test", "lit.cfg"))