Merge #298: cmake: Implement prefix maps

fce102f fixup! cmake: Add `ccache` support (Hennadii Stepanov)

Pull request description:

  This PR implements the following Autotools functionality: https://github.com/hebasto/bitcoin/blob/f63b2002a1dcb53178626147d61bfd290e63d65b/configure.ac#L1481-L1484

  Fixes #297.

Top commit has no ACKs.

Tree-SHA512: 0fcadc62cc864567c7726a5173702199a4bfec152cff1d33b9839efbfb22f9c63a67521ea537b1632521206f1ec9a296806128f47bc297cf3700814a319c970e

cmake/ccache.cmake

@@ -17,6 +17,12 @@ if(NOT MSVC)
       list(APPEND CMAKE_C_COMPILER_LAUNCHER ${CCACHE_EXECUTABLE})
       list(APPEND CMAKE_CXX_COMPILER_LAUNCHER ${CCACHE_EXECUTABLE})
     endif()
+    try_append_cxx_flags("-fdebug-prefix-map=A=B" TARGET core_interface SKIP_LINK
+      IF_CHECK_PASSED "-fdebug-prefix-map=${PROJECT_SOURCE_DIR}=."
+    )
+    try_append_cxx_flags("-fmacro-prefix-map=A=B" TARGET core_interface SKIP_LINK
+      IF_CHECK_PASSED "-fmacro-prefix-map=${PROJECT_SOURCE_DIR}=."
+    )
   else()
     set(WITH_CCACHE OFF)
   endif()