feat: pkgconfig and fix default CFLAGS

Makefile.am

@@ -11,3 +11,6 @@ pkginclude_HEADERS = \
 	include/cli.h \
 	include/cli_parse_utils.h \
 	include/compiler.h
+
+pkgconfigdir = $(libdir)/pkgconfig
+pkgconfig_DATA = libcli.pc

configure.ac

@@ -4,6 +4,10 @@ AC_CONFIG_AUX_DIR([build-aux])
 AC_CONFIG_MACRO_DIRS([m4])
 AM_INIT_AUTOMAKE([foreign -Wall -Werror subdir-objects])
 AC_PROG_CC
+if test "x$ac_cv_env_CFLAGS_set" != "xset"; then
+  CFLAGS="-O2"
+fi
+
 AM_PROG_AR
 
 LT_PREREQ([2.2])
@@ -33,6 +37,7 @@ AC_CONFIG_FILES([
 	src/Makefile
 	tests/Makefile
 	example/Makefile
+	libcli.pc
 ])
 AC_OUTPUT
 
@@ -45,3 +50,4 @@ AC_MSG_NOTICE([
   CFLAGS : $CFLAGS
   tests  : $enable_tests
 ])
+

libcli.pc.in

@@ -0,0 +1,10 @@
+prefix=@prefix@
+exec_prefix=@exec_prefix@
+libdir=@libdir@
+includedir=@includedir@
+
+Name: libcli
+Description: Small CLI parsing library
+Version: @PACKAGE_VERSION@
+Libs: -L${libdir} -lcli
+Cflags: -I${includedir}