Merge remote-tracking branch 'CajuM/PR-headers_install' into testing

diff --cc Makefile
index b936d11e5d09ba75e7133f95c50cd8e9de168556,65a0244a8427359ac5900e8784906127955bcaba..6b1d9bc85a8f254f5cc2fbb82b2c0dc9fba51725
--- 1/Makefile
--- 2/Makefile
+++ b/Makefile
@@@ -786,9 -758,9 +786,9 @@@ $(foreach _D,$(UK_DEPS) $(UK_DEPS-y),
  endif
  
  # include Makefile for platform linking (`Linker.uk`)
 -$(foreach plat,$(UK_PLATS),$(eval $(call _import_linker,$(plat))))
 +$(foreach plat,$(UK_PLATS),$(eval $(call import_linker,$(plat))))
  
- .PHONY: prepare preprocess image libs objs clean
+ .PHONY: prepare preprocess headers_install image libs objs clean
  
  fetch: $(UK_FETCH) $(UK_FETCH-y)