build: Support SYSROOT based config script finding.
* src/libgcrypt.m4: Add support for SYSROOT and set gpg_config_script_warn. Use AC_PATH_PROG instead of AC_PATH_TOOL because the config script is not expected to be installed with a prefix for its name * configure.ac: Print a library mismatch warning. * m4/gpg-error.m4: Update from git master.
Also fixed the false copyright notice in libgcrypt.m4.