[PULL 19/28] configure: preserve PKG_CONFIG for subdir builds

[Alex Bennée]

The slirp sub-module complains about not being able to find the glib
library on cross-compiles because it is using the default pkg-config
tool (which isn't installed in our cross-build docker images).
Preserve PKG_CONFIG in our host config and pass it down to slirp.

Signed-off-by: Alex Bennée <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

diff --git a/Makefile b/Makefile
index a0c1430b40..8da33595ed 100644
--- a/Makefile
+++ b/Makefile
@@ -510,7 +510,11 @@ capstone/all: .git-submodule-status
 
 .PHONY: slirp/all
 slirp/all: .git-submodule-status
-       $(call quiet-command,$(MAKE) -C $(SRC_PATH)/slirp 
BUILD_DIR="$(BUILD_DIR)/slirp" CC="$(CC)" AR="$(AR)" LD="$(LD)" 
RANLIB="$(RANLIB)" CFLAGS="$(QEMU_CFLAGS) $(CFLAGS)" LDFLAGS="$(LDFLAGS)")
+       $(call quiet-command,$(MAKE) -C $(SRC_PATH)/slirp               \
+               BUILD_DIR="$(BUILD_DIR)/slirp"                  \
+               PKG_CONFIG="$(PKG_CONFIG)"                              \
+               CC="$(CC)" AR="$(AR)"   LD="$(LD)" RANLIB="$(RANLIB)"   \
+               CFLAGS="$(QEMU_CFLAGS) $(CFLAGS)" LDFLAGS="$(LDFLAGS)")
 
 # Compatibility gunk to keep make working across the rename of targets
 # for recursion, to be removed some time after 4.1.
diff --git a/configure b/configure
index 397bb476e1..542f6aea3f 100755
--- a/configure
+++ b/configure
@@ -7302,6 +7302,7 @@ echo "OBJCOPY=$objcopy" >> $config_host_mak
 echo "LD=$ld" >> $config_host_mak
 echo "RANLIB=$ranlib" >> $config_host_mak
 echo "NM=$nm" >> $config_host_mak
+echo "PKG_CONFIG=$pkg_config_exe" >> $config_host_mak
 echo "WINDRES=$windres" >> $config_host_mak
 echo "CFLAGS=$CFLAGS" >> $config_host_mak
 echo "CFLAGS_NOPIE=$CFLAGS_NOPIE" >> $config_host_mak
-- 
2.20.1