build: Drop non-existent share/pkgconfig directory

depends/packages/qt.mk

@@ -248,7 +248,6 @@ endef
 define $(package)_config_cmds
   export PKG_CONFIG_SYSROOT_DIR=/ && \
   export PKG_CONFIG_LIBDIR=$(host_prefix)/lib/pkgconfig && \
-  export PKG_CONFIG_PATH=$(host_prefix)/share/pkgconfig && \
   cd qtbase && \
   ./configure -top-level $($(package)_config_opts)
 endef