message: Test installing in a non-standard location.
  Also
  * remove unnecessary dependency on 'release' in make_install
  target.
  * make sure 'make clean' also cleans test install directory.
diff: @@ -84,12 +84,12 @@ regression: release
  pushd build && tclsh ../tests/regression.tcl diff_mode show_diff && popd
  clean:
  - $(RM) -r build dbuild coverage-build dist
  + $(RM) -r build dbuild coverage-build dist tests/TestInstall/build
  install: release
  cmake --install build
  -test_install: release
  +test_install:
  cmake -DCMAKE_BUILD_TYPE=Release -DINSTALL_DIR=$(PREFIX) -S tests/TestInstall -B tests/TestInstall/build
  cmake --build tests/TestInstall/build -j $(CPU_CORES)
  