Add ability to set CMake options with env variables

Author: saghul

CMakeLists.txt

@@ -51,15 +51,27 @@ else()
     add_compile_options(-g)
 endif()
 
-option(BUILD_SHARED_LIBS "Build a shared library" OFF)
+macro(xoption OPTION_NAME OPTION_TEXT OPTION_DEFAULT)
+    option(${OPTION_NAME} ${OPTION_TEXT} ${OPTION_DEFAULT})
+    if(DEFINED ENV{${OPTION_NAME}})
+        # Allow setting the option through an environment variable.
+        set(${OPTION_NAME} $ENV{${OPTION_NAME}})
+    endif()
+    if(${OPTION_NAME})
+        add_definitions(-D${OPTION_NAME})
+    endif()
+    message(STATUS "  ${OPTION_NAME}: ${${OPTION_NAME}}")
+endmacro()
+
+xoption(BUILD_SHARED_LIBS "Build a shared library" OFF)
 if(BUILD_SHARED_LIBS)
     message(STATUS "Building a shared library")
 endif()
 
-option(BUILD_EXAMPLES "Build examples" OFF)
-option(CONFIG_ASAN "Enable AddressSanitizer (ASan)" OFF)
-option(CONFIG_MSAN "Enable MemorySanitizer (MSan)" OFF)
-option(CONFIG_UBSAN "Enable UndefinedBehaviorSanitizer (UBSan)" OFF)
+xoption(BUILD_EXAMPLES "Build examples" OFF)
+xoption(CONFIG_ASAN "Enable AddressSanitizer (ASan)" OFF)
+xoption(CONFIG_MSAN "Enable MemorySanitizer (MSan)" OFF)
+xoption(CONFIG_UBSAN "Enable UndefinedBehaviorSanitizer (UBSan)" OFF)
 
 if(CONFIG_ASAN)
 message(STATUS "Building with ASan")