Make test suite optional by using CTest

CMakeLists.txt

@@ -15,6 +15,9 @@ option(ENABLE_HLSL "Enables HLSL input support" ON)
 
 project(glslang)
 
+# make testing optional
+include(CTest)
+
 if(ENABLE_AMD_EXTENSIONS)
     add_definitions(-DAMD_EXTENSIONS)
 endif(ENABLE_AMD_EXTENSIONS)

External/CMakeLists.txt

 # Suppress all warnings from external projects.
 set_property(DIRECTORY APPEND PROPERTY COMPILE_OPTIONS -w)
 
-if (TARGET gmock)
+if(BUILD_TESTING)
+    if(TARGET gmock)
         message(STATUS "Google Mock already configured - use it")
-elseif(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/googletest)
+    elseif(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/googletest)
         # We need to make sure Google Test does not mess up with the
         # global CRT settings on Windows.
         if(WIN32)
@@ -27,7 +28,8 @@ elseif(IS_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}/googletest)
             gtest_disable_pthreads
             gtest_force_shared_crt
             gtest_hide_internal_symbols)
-else()
+    else()
         message(STATUS
             "Google Mock was not found - tests based on that will not build")
+    endif()
 endif()

gtests/CMakeLists.txt

-if (TARGET gmock)
+if(BUILD_TESTING)
+    if(TARGET gmock)
         message(STATUS "Google Mock found - building tests")
 
         set(TEST_SOURCES
@@ -52,4 +53,5 @@ if (TARGET gmock)
 
         add_test(NAME glslang-gtests
                  COMMAND glslangtests --test-root "${GLSLANG_TEST_DIRECTORY}")
+    endif()
 endif()