[PATCH] Fix bug: Don't clobber `PKG_CONFIG' when overriding pkg-config search for bdw-gw.

[Thien-Thi Nguyen <ttn@gnuvola.org>]

`PKG_CONFIG' is AC_SUBSTed into one of the "make installcheck" tests,
so clobbering it results in "make installcheck" failure.

With this change (and building upon previously submitted patches), i can:

$ .../configure -C \
    --with-threads \
    --prefix /tmp/a/b/z \
    BDW_GC_LIBS='-lgc' \
    LDFLAGS='-L/home/ttn/local/lib'
$ make all check install installcheck

to an empty /tmp/a/b/z directory on a Debian Etch Sempron (~35 minutes).
Moving right along!

thi

_____________________________________________________________________________
From d6d765a2fcb0354146be6492a1212d5ad45fa385 Mon Sep 17 00:00:00 2001
From: Thien-Thi Nguyen <ttn@gnuvola.org>
Date: Sat, 9 Jan 2010 22:40:10 +0100
Subject: [PATCH] Fix bug: Don't clobber `PKG_CONFIG' when overriding pkg-config search for bdw-gw.

* configure.ac (PKG_PROG_PKG_CONFIG): New top-level call.
(PKG_CHECK_MODULES): Call only if both vars `BDW_GC_FLAGS'
and `BDW_GC_LIBS' have no, or empty, value.
* README: Remove bogus advice to specify "PKG_CONFIG=true".

Signed-off-by: Thien-Thi Nguyen <ttn@gnuvola.org>
---
 README       |    3 ---
 configure.ac |    9 ++++++++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/README b/README
index e799495..55bfad2 100644
--- a/README
+++ b/README
@@ -99,10 +99,7 @@ Guile requires the following external packages:
     .pc file, you can work around this by setting some environment
     as part of the configure command-line:
 
-    - PKG_CONFIG=true
-
     - BDW_GC_CFLAGS=<compile flags for picking up libgc headers>
-
     - BDW_GC_LIBS=<linker flags for picking up the libgc library>
 
 
diff --git a/configure.ac b/configure.ac
index 78c6418..20e2d62 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1222,7 +1222,14 @@ main ()
 # Boehm's GC library
 #
 #--------------------------------------------------------------------
-PKG_CHECK_MODULES([BDW_GC], [bdw-gc])
+dnl See note for PKG_CHECK_MODULES in aclocal.m4.
+PKG_PROG_PKG_CONFIG
+if test "$BDW_GC_CFLAGS" || test "$BDW_GC_LIBS" ; then :
+  dnl We don't need to declare those env vars precious;
+  dnl PKG_CHECK_MODULES does that.
+else
+  PKG_CHECK_MODULES([BDW_GC], [bdw-gc])
+fi
 
 CFLAGS="$BDW_GC_CFLAGS $CFLAGS"
 LIBS="$BDW_GC_LIBS $LIBS"
-- 
1.6.3.2