Libguestfs - Feb 2018 - [PATCH hivex] ocaml: Link the C bindings with LDFLAGS (RHBZ#1548536).

Use the ocamlmklib -ldopt flag to pass the general $(LDFLAGS) when
calling gcc to link dllmlhivex.so.  We were already passing $(CFLAGS)
when building the object file.

When building using Fedora's standard hardening flags this gives:

ocamlmklib -o mlhivex hivex_c.o hivex.cmo \
    -verbose -ldopt '-Wl,-z,relro
-specs=/usr/lib/rpm/redhat/redhat-hardened-ld' \
    -L../lib/.libs -lhivex
+ gcc -shared  -o ./dllmlhivex.so hivex_c.o  -Wl,-z,relro
-specs=/usr/lib/rpm/redhat/redhat-hardened-ld  -L../lib/.libs -lhivex
+ ar rc ./libmlhivex.a  hivex_c.o; ranlib ./libmlhivex.a
+ /usr/bin/ocamlc -a    -o mlhivex.cma  hivex.cmo -dllib -lmlhivex -cclib
-lmlhivex   -cclib -L../lib/.libs -cclib -lhivex

This also works if $(LDFLAGS) is empty, because ocamlmklib ignores
-ldopt ''.
---
 ocaml/Makefile.am | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/ocaml/Makefile.am b/ocaml/Makefile.am
index 61db095..85655b6 100644
--- a/ocaml/Makefile.am
+++ b/ocaml/Makefile.am
@@ -41,10 +41,14 @@ OBJS = hivex_c.o hivex.cmo
 XOBJS = $(OBJS:.cmo=.cmx)
 
 mlhivex.cma: $(OBJS)
-	$(OCAMLMKLIB) -o mlhivex $^ -L$(top_builddir)/lib/.libs -lhivex
+	$(OCAMLMKLIB) -o mlhivex $^ \
+	    -ldopt '$(LDFLAGS)' \
+	    -L$(top_builddir)/lib/.libs -lhivex
 
 mlhivex.cmxa: $(XOBJS)
-	$(OCAMLMKLIB) -o mlhivex $^ -L$(top_builddir)/lib/.libs -lhivex
+	$(OCAMLMKLIB) -o mlhivex $^ \
+	    -ldopt '$(LDFLAGS)' \
+	    -L$(top_builddir)/lib/.libs -lhivex
 
 hivex_c.o: hivex_c.c
 	$(CC) $(AM_CPPFLAGS) $(CFLAGS) -fPIC -Wall -c $<
-- 
2.13.2