On GNU-compatible compilers, avoid embedding paths into binaries.

This is helpful for reproducible builds, and also makes it easier
to debug binaries built on another system.

CMakeLists.txt

@@ -66,6 +66,13 @@ endif()
 
 # common compiler flags
 
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+    set(DEBUG_FLAGS "-fdebug-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}=.")
+    set(DEBUG_FLAGS "${DEBUG_FLAGS} -ffile-prefix-map=${CMAKE_CURRENT_SOURCE_DIR}=.")
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${DEBUG_FLAGS}")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${DEBUG_FLAGS}")
+endif()
+
 if(MINGW)
     set(CMAKE_C_FLAGS   "${CMAKE_C_FLAGS} -static-libgcc")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -static-libgcc -static-libstdc++")