external-arm-toolchain: remove ${base_libdir}/libpthread*.so from FILES:${PN}

When `usrmerge` distro feature is not enabled, then `${base_libdir}`
resolves to `/lib` and `/lib/libpthread*.so` does not match any files.
But, with `usrmerge` distro feature, `${base_libdir}` is `/usr/lib`, so
removed line leads to `/usr/lib/libpthread.so` symlink included in
`${PN}` which causes QA check failure.

(cherry picked from commit 8634bdc2f21e1b2801435ecc7b6f7aacde8a7a00)

Signed-off-by: Vasyl Vavrychuk <vvavrychuk@gmail.com>
Acked-by: Denys Dmytriyenko <denys@konsulko.com>
Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Jon Mason <jon.mason@arm.com>

meta-arm-toolchain/recipes-devtools/external-arm-toolchain/external-arm-toolchain.bb

@@ -546,7 +546,6 @@ FILES:${PN} += "\
 	${base_libdir}/ld*.so.* \
 	${base_libdir}/ld-*.so \
 	${base_libdir}/libpthread*.so.* \
-	${base_libdir}/libpthread*.so \
 	${base_libdir}/libpthread-*.so \
 	${base_libdir}/libresolv*.so.* \
 	${base_libdir}/libresolv-*.so \