Fix initramfs hook for merged /usr/lib and /lib

Fix initramfs hook for merged /usr/lib and /lib

Under a merged `/lib` -> `/usr/lib` which renders `/lib` as a symlink,
`find /lib -type f -name libgcc_s.so.1` will not return a result as
`find` will not traverse the symlink. Modifying it to `find /lib/ -type
f -name libgcc_s.so.1` should work for both symlinked and non-symlinked
`/lib` directories.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Matt Kemp <matt@mattikus.com>
Closes #5834