Avoid building test support programs by default with CMake (#1244)

Copy CMake-built test executables to test directory

Fixes CI failures on Windows.
CI should also have failed on Unices, but it turns out
we instead merely hit the fallback that the `make` path
relies on (building those executables with `make`),
which fails on Windows since `make` is not set up to
find libpng.

.github/workflows/testing.yml

@@ -41,6 +41,7 @@ jobs:
           cmake --build build -j --verbose
           cp build/src/rgb{asm,link,fix,gfx} .
           sudo cmake --install build --verbose
+          cmake --install build --verbose --component "Test support programs"
       - name: Package binaries
         run: |
           mkdir bins
@@ -122,6 +123,7 @@ jobs:
           cmake -S . -B build -A ${{ matrix.platform }} -DCMAKE_INSTALL_PREFIX=install_dir -DCMAKE_BUILD_TYPE=Release -DZLIB_LIBRARY="$PWD"/install_dir/lib/zlib.lib -DZLIB_INCLUDE_DIR="$PWD"/install_dir/include -DPNG_LIBRARY="$PWD"/install_dir/lib/libpng16.lib -DPNG_INCLUDE_DIR="$PWD"/install_dir/include
           cmake --build build --config Release -j --verbose
           cmake --install build --verbose --prefix install_dir
+          cmake --install build --verbose --component "Test support programs"
       - name: Package binaries
         shell: bash
         run: |