[CMake] Run git describe from the source dir, fix out-of-tree builds (#3199)

Don't rely on build being same or underneath the source directory.

Fixes #3175.

cmake/modules/GenVersionFile.cmake

@@ -2,8 +2,9 @@
 # Input variables:
 #   IN_FILE             - An absolute path of Version.cpp.in
 #   OUT_FILE            - An absolute path of Version.cpp
-#   RELEASE_PATTERN      - A pattern to search release tags
+#   RELEASE_PATTERN     - A pattern to search release tags
 #   DRY_RUN             - If true, make the version unknown.
+#   SOURCE_ROOT         - Path to root directory of source
 
 set(GIT_DESCRIBE_DEFAULT "unknown git version")
 if (DRY_RUN)
@@ -13,6 +14,7 @@ else ()
   find_package(Git QUIET)
   if (Git_FOUND)
     execute_process(COMMAND ${GIT_EXECUTABLE} describe --dirty --tags --match ${RELEASE_PATTERN}
+      WORKING_DIRECTORY "${SOURCE_ROOT}"
       RESULT_VARIABLE GIT_OUTPUT_RESULT
       OUTPUT_VARIABLE GIT_DESCRIBE_OUTPUT
       OUTPUT_STRIP_TRAILING_WHITESPACE)

lib/Support/CMakeLists.txt

@@ -32,12 +32,14 @@ if (CIRCT_RELEASE_TAG_ENABLED)
     DEPENDS "${CIRCT_GIT_LOGS_HEAD}" "${GEN_VERSION_SCRIPT}"
     COMMAND ${CMAKE_COMMAND} -DIN_FILE="${CMAKE_CURRENT_SOURCE_DIR}/Version.cpp.in"
     -DOUT_FILE="${VERSION_CPP}" -DRELEASE_PATTERN=${CIRCT_RELEASE_TAG}*
-    -DDRY_RUN=OFF -P "${GEN_VERSION_SCRIPT}")
+    -DDRY_RUN=OFF -DSOURCE_ROOT="${CMAKE_SOURCE_DIR}"
+    -P "${GEN_VERSION_SCRIPT}")
 else ()
   # If the release tag generation is disabled, run the script only at the first
   # cmake configuration.
   add_custom_command(OUTPUT "${VERSION_CPP}"
     DEPENDS "${GEN_VERSION_SCRIPT}"
     COMMAND ${CMAKE_COMMAND} -DIN_FILE="${CMAKE_CURRENT_SOURCE_DIR}/Version.cpp.in"
-    -DOUT_FILE="${VERSION_CPP}" -DDRY_RUN=ON -P "${GEN_VERSION_SCRIPT}")
+    -DOUT_FILE="${VERSION_CPP}" -DDRY_RUN=ON -DSOURCE_ROOT="${CMAKE_SOURCE_DIR}"
+    -P "${GEN_VERSION_SCRIPT}")
 endif()