Add variable to indicate external headers #35

Job	Run time
Select platforms	1s
alpine-linux-x64	0s
docs / build (debug)	2m 6s
linux-cross-compile / build (aarch64)	3m 57s
linux-x64 / build (debug)	2m 5s
linux-cross-compile / build (arm)	4m 8s
linux-cross-compile / build (s390x)	3m 38s
linux-x64 / build (release)	2m 42s
linux-cross-compile / build (ppc64le)	4m 19s
linux-x64-hs-minimal / build (debug)	1m 39s
linux-cross-compile / build (riscv64)	15m 43s
linux-x64-hs-nopch / build (debug)	1m 32s
linux-x64-hs-optimized / build (debug)	1m 22s
linux-x64-hs-zero / build (debug)	2m 29s
linux-x86-hs / build (debug)	2m 28s
linux-x86-hs / build (release)	3m 36s
macos-x64 / build (debug)	2m 47s
macos-aarch64 / build (debug)	3m 53s
windows-aarch64 / build (debug)	3m 52s
macos-x64 / build (release)	2m 36s
windows-aarch64 / build (release)	3m 37s
windows-x64 / build (debug)	2m 57s
macos-aarch64 / build (release)	1m 32s
windows-x64 / build (release)	4m 53s
linux-x64	0s
macos-x64	0s
macos-aarch64	0s
windows-x64	0s
Remove bundle artifacts	4s
	1h 17m 56s

Provide feedback