configure: Detect linking style for HP aCC on HP-UX

HP aCC does not accept any of the previously tested CC_LD_DYNPATH
formats, but only its own[1] "-Wl,+b" format. Add it to configure.ac.

1. http://nixdoc.net/man-pages/hp-ux/man1/ld_pa.1.html

Signed-off-by: Michael Osipov <michael.osipov@siemens.com>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

configure.ac

@@ -475,8 +475,18 @@ else
       if test "$git_cv_ld_rpath" = "yes"; then
          CC_LD_DYNPATH=-rpath
       else
-         CC_LD_DYNPATH=
-         AC_MSG_WARN([linker does not support runtime path to dynamic libraries])
+         AC_CACHE_CHECK([if linker supports -Wl,+b,], git_cv_ld_wl_b, [
+            SAVE_LDFLAGS="${LDFLAGS}"
+            LDFLAGS="${SAVE_LDFLAGS} -Wl,+b,/"
+            AC_LINK_IFELSE([AC_LANG_PROGRAM([], [])], [git_cv_ld_wl_b=yes], [git_cv_ld_wl_b=no])
+            LDFLAGS="${SAVE_LDFLAGS}"
+         ])
+         if test "$git_cv_ld_wl_b" = "yes"; then
+            CC_LD_DYNPATH=-Wl,+b,
+          else
+             CC_LD_DYNPATH=
+             AC_MSG_WARN([linker does not support runtime path to dynamic libraries])
+          fi
       fi
    fi
 fi