• Fix build on 9.x (extract of build error, below)
• Replace CPPFLAGS and LDFLAGS by USES= localbase

checking for ZLIB... no
configure: error: Package requirements (zlib >= 1.2.0) were not met:

Package zlib was not found in the pkg-config search path.
Perhaps you should add the directory containing `zlib.pc'
to the PKG_CONFIG_PATH environment variable
Package 'zlib', required by 'world', not found

Consider adjusting the PKG_CONFIG_PATH environment variable if you
installed software in a non-standard prefix.

Alternatively, you may set the environment variables ZLIB_CFLAGS
and ZLIB_LIBS to avoid the need to call pkg-config.