python3: install pkgconfig to staging

Some programs that use the Python C API have difficulties finding
cross-compiled Python3 without the pkgconfig, so make sure we have
python3.pc and python-3.7.pc in pkgconfig staging dir.

CircleCI requires a package Makefile change to actually
do the CI check, so bump PKG_RELEASE.

Signed-off-by: Daniel F. Dickinson <cshored@thecshore.com>

lang/python/python3/Makefile

@@ -14,7 +14,7 @@ PYTHON_VERSION:=$(PYTHON3_VERSION)
 PYTHON_VERSION_MICRO:=$(PYTHON3_VERSION_MICRO)
 
 PKG_NAME:=python3
-PKG_RELEASE:=2
+PKG_RELEASE:=3
 PKG_VERSION:=$(PYTHON_VERSION).$(PYTHON_VERSION_MICRO)
 
 PKG_SOURCE:=Python-$(PKG_VERSION).tar.xz
@@ -197,6 +197,7 @@ endef
 define Build/InstallDev
 	$(INSTALL_DIR) $(1)/usr/include/ $(1)/usr/lib/
 	$(INSTALL_DIR) $(1)/usr/lib/python$(PYTHON_VERSION)/
+	$(INSTALL_DIR) $(1)/usr/lib/pkgconfig
 	$(CP) \
 		$(PKG_INSTALL_DIR)/usr/include/python$(PYTHON_VERSION) \
 		$(1)/usr/include/
@@ -204,6 +205,10 @@ define Build/InstallDev
 		$(HOST_PYTHON3_LIB_DIR) \
 		$(PKG_INSTALL_DIR)/usr/lib/libpython$(PYTHON_VERSION).so* \
 		$(1)/usr/lib/
+	$(CP) \
+		$(PKG_INSTALL_DIR)/usr/lib/pkgconfig/python3.pc \
+		$(PKG_INSTALL_DIR)/usr/lib/pkgconfig/python-$(PYTHON3_VERSION).pc \
+		$(1)/usr/lib/pkgconfig
 	$(CP) \
 		$(PKG_INSTALL_DIR)/usr/lib/python$(PYTHON_VERSION)/config-$(PYTHON_VERSION) \
 		$(1)/usr/lib/python$(PYTHON_VERSION)/