configure: Use pkg-config for jimtcl

The jimtcl project supports pkg-config, use it for a simpler
configuration of compiler and linker flags and to enforce the minimum
required package version.

Since the jimtcl pkg-config file is not available on all systems, use
AC_CHECK_HEADER() as fallback.

Change-Id: I6fdcc818a8fdd205a126b0a46356434dbe890226
Signed-off-by: Marc Schink <dev@zapb.de>
Reviewed-on: https://review.openocd.org/c/openocd/+/8383
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

Makefile.am

@@ -48,6 +48,8 @@ AM_CPPFLAGS = $(HOST_CPPFLAGS)\
 if INTERNAL_JIMTCL
 AM_CPPFLAGS += -I$(top_srcdir)/jimtcl \
 			   -I$(top_builddir)/jimtcl
+else
+AM_CPPFLAGS += $(JIMTCL_CFLAGS)
 endif
 EXTRA_DIST += \
 	BUGS \

configure.ac

@@ -594,6 +594,15 @@ AS_IF([test "x$use_internal_jimtcl" = "xyes"], [
   ], [
     AC_MSG_ERROR([jimtcl not found, run git submodule init and git submodule update.])
   ])
+], [
+  PKG_CHECK_MODULES([JIMTCL], [jimtcl >= 0.79], [
+      have_jimtcl_pkg_config=yes
+    ], [
+      have_jimtcl_pkg_config=no
+      AC_CHECK_HEADER([jim.h], [], [
+        AC_MSG_ERROR([jimtcl is required but not found via pkg-config and system includes])
+      ])
+  ])
 ])
 
 AS_IF([test "x$build_remote_bitbang" = "xyes"], [
@@ -781,6 +790,7 @@ AM_CONDITIONAL([DMEM], [test "x$build_dmem" = "xyes"])
 AM_CONDITIONAL([HAVE_CAPSTONE], [test "x$enable_capstone" != "xno"])
 
 AM_CONDITIONAL([INTERNAL_JIMTCL], [test "x$use_internal_jimtcl" = "xyes"])
+AM_CONDITIONAL([HAVE_JIMTCL_PKG_CONFIG], [test "x$have_jimtcl_pkg_config" = "xyes"])
 AM_CONDITIONAL([INTERNAL_LIBJAYLINK], [test "x$use_internal_libjaylink" = "xyes"])
 
 # Look for environ alternatives.  Possibility #1: is environ in unistd.h or stdlib.h?

src/Makefile.am

@@ -17,8 +17,12 @@ bin_PROGRAMS += %D%/openocd
 if INTERNAL_JIMTCL
 %C%_openocd_LDADD += $(top_builddir)/jimtcl/libjim.a
 else
+if HAVE_JIMTCL_PKG_CONFIG
+%C%_openocd_LDADD += $(JIMTCL_LIBS)
+else
 %C%_openocd_LDADD += -ljim
 endif
+endif
 
 %C%_libopenocd_la_CPPFLAGS =