Merge pull request #226 from drwells/prevent-in-source-builds

Prevent in-source builds.

Author: drwells

CMakeLists.txt

@@ -1,5 +1,13 @@
 CMAKE_MINIMUM_REQUIRED(VERSION 3.15.0)
 
+# Do this before project() to skip the compiler config process
+IF("${CMAKE_BINARY_DIR}" STREQUAL "${CMAKE_SOURCE_DIR}")
+  MESSAGE(FATAL_ERROR "This project does not support in-source builds.
+    Please create a subfolder and use `cmake ..` inside it.
+    NOTE: cmake will now create CMakeCache.txt and CMakeFiles/*.
+          You must delete them, or cmake will refuse to work.")
+ENDIF()
+
 # Major version of fiddle. Our convention is that X.0 is a development version
 # and X.1, X.2, etc. are release versions.
 SET(FDL_VERSION_MAJOR 4)