When a package declares a PKG_BUILD_DEPENDENCY or HOST_BUILD_DEPENDENCY on
a not existing build type, the metadata script will emit a reference to an
unresolvable build target in tmp/.packagedeps, causing the make process to
fail hard in a way not catchable by the IGNORE_ERRORS mechanism.
In a situation where a package "test-a" declares a build dependency
"PKG_BUILD_DEPENDS:=test-b/host" while the Makefile of "test-b" does not
implement a HostBuild, make fails with an unrecoverable error in the form:
make[1]: Entering directory '...'
make[1]: *** No rule to make target 'package/test-b/host/compile',
needed by 'package/test-a/compile'. Stop.
make[1]: Leaving directory '...'
.../toplevel.mk:200: recipe for target 'package/test-a/compile' failed
make: *** [package/test-a/compile] Error 2
Extend the metadata generation script to catch such unresolved references
and emit a visable warning upon detection.
After this change, the script will emit a warning similar to:
WARNING: Makefile "package/test-a/Makefile" has a build dependency on
"test-b/host" but "package/test-b/Makefile" does not implement a
"host" build type
Fixes a global build cluster outage which occured after the "python-cffi"
feed package removed its HostBuild which the "python-cryptography" package
build-depended on.
Signed-off-by: Jo-Philipp Wich <jo@mein.io>