A user reported a build failure with portmaster. I was able to
deduce he had lang/gcc48 installed and reproduce the build error
in a poudriere jail:

/usr/local/lib/gcc48/libstdc++.so.6: version CXXABI_1.3.9 required by /usr/local/xtensa-esp32-elf/bin/xtensa-esp32-elf-gcc not found

He also reported that the binaries from the FreeBSD built package
produced this error.

The fix is explicitly set LD_RUN_PATH to the gcc lib directory.

Reported by: danny@cs.huji.ac.il
Reviewed by: ler (mentor)
Approved by: ler (mentor)
Differential Revision: https://reviews.freebsd.org/D16477