Hi Thomas I'm seeing a similar (but not identical) issue[1] which is also related to the subdir-objects commit[2] when building the package "Heimdal" with automake-1.16+ (and GNU make-4.2.1).
Making all in hcrypto make[2]: Entering directory '/home/abuild/rpmbuild/BUILD/heimdal-7.5.0/lib/hcrypto' CC test_rand.o In file included from test_rand.c:42: rand.h:46:10: fatal error: hcrypto/engine.h: No such file or directory #include <hcrypto/engine.h> ^~~~~~~~~~~~~~~~~~ compilation terminated. make[2]: *** [Makefile:2064: test_rand.o] Error 1 make[2]: Leaving directory '/home/abuild/rpmbuild/BUILD/heimdal-7.5.0/lib/hcrypto' make[1]: *** [Makefile:564: all-recursive] Error 1 Heimdal builds fine with automake-1.15.1, but Heimdal fails as above with automake-1.16 (and 1.16.1), and it also fails with automake-1.15.1 + the subdir-objects commit[2]. At the moment I've no idea if this is a Heimdal issue (bug/bad practice in Makefile[3]?), or an automake-1.16.1 regression, so any input would be appreciated! Thanks Neil MacLeod (MilhouseVH) 1. https://github.com/heimdal/heimdal/issues/529 2. http://git.savannah.gnu.org/cgit/automake.git/commit/?id=f4e91bfc490da63209aad19636568da3b955dcd4&h=master 3. https://github.com/heimdal/heimdal/blob/master/lib/hcrypto/Makefile.am