Don't build libxslt.dll against debugging runtime for --enable-debug

Same problem as a few commits earlier: libxslt's configure.js uses
debug=yes to mean using the debugging crt, which we don't want in just
a debug=t build. (And which will make libxslt.dll fail to load.) Look
at $(dbgutil), not $(debug). (And note that in general dbgutil builds
are disabled for Windows currently anyway.)

libxslt/makefile.mk

@@ -93,7 +93,7 @@ BUILD_DIR=$(CONFIGURE_DIR)
 CONFIGURE_DIR=win32
 CONFIGURE_ACTION=cscript configure.js
 #CONFIGURE_FLAGS=iconv=no sax1=yes
-.IF "$(debug)"!=""
+.IF "$(dbgutil)"!=""
 CONFIGURE_FLAGS+=debug=yes
 .ENDIF
 BUILD_ACTION=nmake