cmake: Add easy sanitizers option

Set -DSANITIZE to a comma-separated list of options to pass to
-fsanitize=, like -DSANITIZE=address,undefined

cmake/Sanitizers.cmake

@@ -0,0 +1,8 @@
+set(SANITIZE "" CACHE STRING "Sanitizers to enable.")
+
+string(REGEX MATCHALL "[^,]+" ENABLED_SANITIZERS "${SANITIZE}")
+
+foreach(SANITIZER ${ENABLED_SANITIZERS})
+    add_compile_options("-fsanitize=${SANITIZER}")
+    add_link_options("-fsanitize=${SANITIZER}")
+endforeach()