Parallel buildworld can link OpenSSL engines before libcrypto exists

[laffer1]

A clean parallel world build can fail because the OpenSSL engine subdirectories attempt to link before the parent libcrypto shared library exists.

Reproduction:

env MAKEOBJDIRPREFIX=/tmp/pr500-obj make -j10 buildworld buildkernel

Observed failures:

--- all_subdir_secure/lib/libcrypto/engines/capi ---
ld: error: unable to find library -lcrypto
cc: error: linker command failed with exit code 1
*** [capi.so.full] Error code 1

--- all_subdir_secure/lib/libcrypto/engines/padlock ---
ld: error: unable to find library -lcrypto
cc: error: linker command failed with exit code 1
*** [padlock.so.full] Error code 1

At failure time neither the parent object directory nor the staged sysroot contained libcrypto.so. secure/lib/libcrypto/Makefile declares SUBDIR=engines, while secure/lib/libcrypto/engines/Makefile declares SUBDIR_PARALLEL=. The capi and padlock engine Makefiles use bsd.lib.mk and link against -lcrypto, but the build graph does not ensure that the parent library is available before those parallel links.

An incremental rerun may get past the failure after enough parent-library objects have been retained, which makes this timing-dependent and easy to miss. The dependency/order should be expressed explicitly so a clean -j build succeeds on the first invocation.

This was discovered while validating PR #500, but the PR does not modify the engine Makefiles or their subdirectory ordering.

[laffer1]

Additional confirmation from the same validation run: the race occurs in both the native amd64 library build and the amd64 build32 compatibility pass. In each case, repeated execution first produced libcrypto.so.30.full, then the final library and symlink in the parent object directory, but the engine links still failed because libcrypto had not yet been installed into the active sysroot. Manually installing the already-built parent library with subdirectories disabled allowed both phases to continue. This confirms the dependency cycle is parent install -> engine subdirectories -> -lcrypto from the staged sysroot.