It is much easier if you use GNU Automake instead of writing your own Makefiles. If you do that, you do not have to worry about finding and invoking the libgcrypt-config script at all. Libgcrypt provides an extension to Automake that does all the work for you.
Check whether Libgcrypt (at least version minimum-version, if given) exists on the host system. If it is found, execute action-if-found, otherwise do action-if-not-found, if given.
Additionally, the function defines
LIBGCRYPT_CFLAGSto the flags needed for compilation of the program to find the gcrypt.h header file, and
LIBGCRYPT_LIBSto the linker flags needed to link the program to the Libgcrypt library.
You can use the defined Autoconf variables like this in your Makefile.am:
AM_CPPFLAGS = $(LIBGCRYPT_CFLAGS) LDADD = $(LIBGCRYPT_LIBS)