PKG_CONFIG_LIBDIR = $(INSTALL_DIR)/$(INSTALL_PREFIX)/lib/pkgconfig

INSTALL_DIR = $(WORK_DIR)/install
INSTALL_PREFIX = /usr/local

ENV += LD= CPP= NM= CC= RANLIB= CXX= AR= STRIP= OBJDUM= CFLAGS= CPPFLAGS= LDFLAGS=
ENV += INSTALL_PREFIX=$(INSTALL_PREFIX)

PKG_CONFIG_LIBDIR = $(INSTALL_DIR)/$(INSTALL_PREFIX)/lib/pkgconfig

INSTALL_DIR = $(WORK_DIR)/install
INSTALL_PREFIX = /usr/local

ENV += -u PKG_CONFIG -u PKG_CONFIG_LIBDIR -u PKG_CONFIG_PATH
ENV += LD= CPP= NM= CC= RANLIB= CXX= AR= STRIP= OBJDUM= CFLAGS= CPPFLAGS= LDFLAGS= CXXFLAGS= LDSHARED= READELF= AS= OBJDUMP=
ENV += INSTALL_PREFIX=$(INSTALL_PREFIX)

Fix native env so native python/glibc can be compiled from within spk
Fix native env so native python/glibc can be compiled from within spk

Should prevent reports like #659, #746, #978 etc.
