GN hack to make extensions try to build #16702

Job	Run time
chromium_linux-x64 / initialize	1m 21s
linux / initialize	1m 19s
linux / docker-build-image	3m 34s
chromium_linux-x64 / docker-build-image	3m 31s
linux / x64_devel	6m 8s
linux / x64_debug	6m 10s
linux / x64_qa	6m 3s
linux / x64_gold	5m 35s
chromium_linux-x64 / x64_devel	5m 32s
chromium_linux-x64 / x64_debug	6m 1s
chromium_linux-x64 / x64_qa	6m 13s
chromium_linux-x64 / x64_gold	5m 37s
	57m 4s

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