Added a configure option --with-pkg-config which enables use of pkg-config to aid in the configuration

The spdlog dependency does not propagate its compile flags through config.h in the usual way, causing build failure of the AD when built with spack. When pkg-config is enabled, the configure script now queries that tool for the flags.

Author: giltirn

configure.ac

@@ -6,6 +6,32 @@ AC_PROG_CXX
 AM_PROG_AR
 LT_INIT
 
+#Enable pkg-config
+AC_ARG_WITH([pkg-config], AS_HELP_STRING([--with-pkg-config], [Use pkg-config to determine configuration of some dependencies]),[use_pkgconfig="yes"],[use_pkgconfig="no"])
+
+#Check if pkg-config is installed
+no_pkgconfig=1
+if test "x$use_pkgconfig" != "xno"; then
+    no_pkgconfig=$(echo $(pkg-config 2>&1) | grep -c "not found")
+    if [[ "${no_pkgconfig}" -eq 0 ]]; then
+	AC_MSG_NOTICE([pkg-config was detected])
+    fi
+fi
+
+#spdlog propagates its compile flags through cmake targets and pkg-config but doesn't for autotools
+#thus if pkg-config is available we try to get the flags there
+if [[ "${no_pkgconfig}" -eq 0 ]]; then
+   SPDLOG_CFLAGS=$(pkg-config --cflags spdlog 2>&1)
+   if [[ $(echo ${SPDLOG_CFLAGS} | grep -c "not found") -eq 1 ]]; then
+       AC_MSG_FAILURE(["Cannot find spdlog configuration with pkg-config"])
+   fi
+   CXXFLAGS+="${SPDLOG_CFLAGS}"
+   SPDLOG_LDFLAGS=$(pkg-config --libs spdlog 2>&1)
+   LDFLAGS+="${SPDLOG_LDFLAGS}" 
+   AC_MSG_NOTICE([Retrieved configuration for spdlog from pkg-config])
+fi
+
+
 # Check if compiling to generate a coverage report using gcov
 # Once built, run the tests in the install/test directory, then from the build directory run
 #(pip3 install gcovr)