exclude PGM C API from default build targets #191

Job	Run time
Build sdist and set version	45s
build-cpp-test-linux (debug, gcc)	1m 40s
build-cpp-test-linux (debug, clang)	1m 23s
build-cpp-test-linux (release, gcc)	2m 19s
Build and test in Conda (ubuntu)	1m 2s
build-cpp-test-linux (release, clang)	2m 10s
Build and test in Conda (windows)	5m 50s
build-cpp-test-macos (debug)	1m 2s
build-cpp-test-windows (debug, msvc)	4m 22s
build-cpp-test-macos (release)	1m 38s
build-cpp-test-windows (debug, clang-cl)	4m 14s
build-cpp-test-windows (release, msvc)	4m 36s
build-cpp-test-windows (release, clang-cl)	5m 44s
build-and-test-python (linux-x64)	5m 22s
build-and-test-python (linux-aarch64)	10m 55s
build-and-test-python (macos)	4m 7s
build-and-test-python (windows)	12m 28s
publish-wheels	11s
	1h 9m 48s

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