build: fix linking gen__pfcp_ies_auto to use build-tree libosmo-gtlv

Resolve some confusion in src/libosmo-pfcp/Makefile.am:

It builds
- the libosmo-pfcp library.
- the gen__pfcp_ies_auto tool to be used at build time.

The library has its own LDFLAGS directive, so it does not used the
global AM_LDFLAGS.

So there is no point to have AM_LDFLAGS, and then additional
gen__pfcp_ies_auto__LDADD, just have a gen__pfcp_ies_auto__LDFLAGS.

Put the locally built dependency libosmo-gtlv.la first in this LDFLAGS,
so that libtool takes it from the build tree, not a system installed lib
(if any).

Still keep the AM_CFLAGS, needed for #include paths for building
libosmo-pfcp objects. However, no vty #includes are used, so drop
LIBOSMOVTY_CFLAGS.

Related: OS#5942
Change-Id: I2e92238b214d8e79bab1095d6093139bad05bc66

src/libosmo-pfcp/Makefile.am

@@ -10,17 +10,9 @@ AM_CFLAGS = \
 	-Wall \
 	$(LIBOSMOCORE_CFLAGS) \
 	$(LIBOSMOGSM_CFLAGS) \
-	$(LIBOSMOVTY_CFLAGS) \
 	$(COVERAGE_CFLAGS) \
 	$(NULL)
 
-AM_LDFLAGS = \
-	$(LIBOSMOCORE_LIBS) \
-	$(LIBOSMOGSM_LIBS) \
-	$(LIBOSMOVTY_LIBS) \
-	$(COVERAGE_LDFLAGS) \
-	$(NULL)
-
 lib_LTLIBRARIES = \
 	libosmo-pfcp.la \
 	$(NULL)
@@ -65,8 +57,7 @@ gen__pfcp_ies_auto_SOURCES = \
 	gen__pfcp_ies_auto.c \
 	$(NULL)
 
-gen__pfcp_ies_auto_LDADD = \
+gen__pfcp_ies_auto_LDFLAGS = \
 	$(top_builddir)/src/libosmo-gtlv/libosmo-gtlv.la \
 	$(LIBOSMOCORE_LIBS) \
-	$(COVERAGE_LDFLAGS) \
 	$(NULL)