[Buildroot] [PATCH v1] package/postgis: fix configure in case of host installed libxml2

Explicit set cross-compile xml2-config path to fix configure failure
in case of host installed libxml2 package, otherwise postgis configure
finds the wrong/host xml2-config first.

Fixes:

   checking for xml2-config... /usr/bin/xml2-config
   checking libxml/tree.h usability... no
   checking libxml/tree.h presence... no
   checking for libxml/tree.h... no
   configure: error: could not find headers include related to libxml2

Signed-off-by: Peter Seiderer <redacted>
---
Notes:
   - depends on
     http://patchwork.ozlabs.org/project/buildroot/patch/20210126133908.680621-1-fido_max at inbox.ru/
---
  package/postgis/postgis.mk | 5 ++++-
  1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/package/postgis/postgis.mk b/package/postgis/postgis.mk
index 85102d323a..b2e51b15eb 100644
--- a/package/postgis/postgis.mk
+++ b/package/postgis/postgis.mk

@@ -14,7 +14,10 @@ POSTGIS_AUTORECONF = YES
  
  POSTGIS_DEPENDENCIES = postgresql libgeos proj libxml2
  
-POSTGIS_CONF_OPTS += --with-pgconfig=$(STAGING_DIR)/usr/bin/pg_config --with-geosconfig=$(STAGING_DIR)/usr/bin/geos-config
+POSTGIS_CONF_OPTS += \
+	--with-pgconfig=$(STAGING_DIR)/usr/bin/pg_config \
+	--with-geosconfig=$(STAGING_DIR)/usr/bin/geos-config \
+	--with-xml2config=$(STAGING_DIR)/usr/bin/xml2-config
  
  ifeq ($(BR2_PACKAGE_LIBGDAL),y)
  POSTGIS_DEPENDENCIES += libgdal