Additional fixes for offscreen build in addition to GC+LSP #103

Job	Run time
determine_asy_version	7s
build-asy-windows / configure-windows-msvc-x64	3m 12s
build-asy-linux / configure-linux-release-x64	49s
build-gui / build-gui-windows	30s
build-gui / build-gui-linux	12s
build-asy-linux / build-linux-release-x64	1m 33s
build-asy-linux / linux-asy-docgen	3m 18s
build-asy-windows / build-windows-msvc-x64	6m 52s
build-asy-linux / package-asymptote-artifacts	13s
test-asy-linux / test-x64-cxxtests	34s
test-asy-linux / test-x64-asy-tests	50s
package-asy-install-file / package-asy-installer	49s
test-asy-windows / test-windows-msvc-x64-cxxtests	46s
test-asy-windows / test-windows-msvc-x64-asy-tests	1m 42s
precheck-pass	1s
	21m 28s

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