[gnome-doc-utils] fix nested command substitution

[Shaun McCance <shaunm src gnome org>]

commit 1651a350a8beb68edc3c64cb74ff084e21c2803a
Author: Chris Coleman <chrsclmn gmail com>
Date:   Fri Dec 17 13:35:42 2010 +0000

    fix nested command substitution

 tools/gnome-doc-utils.make |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/tools/gnome-doc-utils.make b/tools/gnome-doc-utils.make
index 97fd549..bc2a61f 100644
--- a/tools/gnome-doc-utils.make
+++ b/tools/gnome-doc-utils.make
@@ -138,7 +138,7 @@ _db2omf  ?= `$(PKG_CONFIG) --variable db2omf gnome-doc-utils`
 _malrng  ?= `$(PKG_CONFIG) --variable malrng gnome-doc-utils`
 _chunks  ?= `$(PKG_CONFIG) --variable xmldir gnome-doc-utils`/gnome/xslt/docbook/utils/chunks.xsl
 _credits ?= `$(PKG_CONFIG) --variable xmldir gnome-doc-utils`/gnome/xslt/docbook/utils/credits.xsl
-_ids ?= `$(PKG_CONFIG) --variable xmldir gnome-doc-utils`/gnome/xslt/docbook/utils/ids.xsl
+_ids ?= $(shell $(PKG_CONFIG) --variable xmldir gnome-doc-utils)/gnome/xslt/docbook/utils/ids.xsl
 
 if ENABLE_SK
 _ENABLE_SK = true