2.3 Building sources using Automake

You can simply use PKG_CHECK_MODULES macro with pkg-config:

PKG_CHECK_MODULES([LIBGCRYPT], [libgcrypt >= 1.11])

Alternatively, instead of using pkg-config, for building on an environment with no pkg-config, libgcrypt also provides an extension to Automake that does all the work for you. Please note that it is required to have gpgrt-config from libgpg-error installed in this case.

Macro: AM_PATH_LIBGCRYPT ([minimum-version], [action-if-found], [action-if-not-found])

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_CFLAGS to the flags needed for compilation of the program to find the gcrypt.h header file, and LIBGCRYPT_LIBS to the linker flags needed to link the program to the Libgcrypt library.

This macro locates for libgcrypt.pc, with cross-compile support.

You can use the defined Autoconf variables like this in your Makefile.am:

AM_CPPFLAGS = $(LIBGCRYPT_CFLAGS)
LDADD = $(LIBGCRYPT_LIBS)