curl -sS -L -O https://www.iana.org/time-zones/repository/releases/tzdata$DATA.tar.gz
tar xzf tzcode$CODE.tar.gz
tar xzf tzdata$DATA.tar.gz

if ! make CFLAGS=-DSTD_INSPIRED AWK=awk TZDIR=zoneinfo posix_only >make.out 2>&1; then
	cat make.out
	exit 2
fi

cd zoneinfo
../mkzip ../../zoneinfo.zip
cd ../..

files="update.bash zoneinfo.zip"
modified=true

effect to systems satisfying one of the constraints
(see https://golang.org/pkg/go/build/#hdr-Build_Constraints for details about the constraint syntax).
For example:

	// #cgo CFLAGS: -DPNG_DEBUG=1
	// #cgo amd64 386 CFLAGS: -DX86=1
	// #cgo LDFLAGS: -lpng
	// #include <png.h>
	import "C"

Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config tool

		return "enum " + t
	}
	if t, ok := strings.CutPrefix(s, "sizeof_"); ok {
		return "sizeof(" + cname(t) + ")"
	}
	return s
}

// ProcessCgoDirectives processes the import C preamble:
//  1. discards all #cgo CFLAGS, LDFLAGS, nocallback and noescape directives,
//     so they don't make their way into _cgo_export.h.
//  2. parse the nocallback and noescape directives.
func (f *File) ProcessCgoDirectives() {