return strings.Join(s, " ")
		}
		return q
	}

	ret := []cfg.EnvVar{
		// Note: Update the switch in runEnv below when adding to this list.
		{Name: "CGO_CFLAGS", Value: join(cflags)},
		{Name: "CGO_CPPFLAGS", Value: join(cppflags)},
		{Name: "CGO_CXXFLAGS", Value: join(cxxflags)},
		{Name: "CGO_FFLAGS", Value: join(fflags)},
		{Name: "CGO_LDFLAGS", Value: join(ldflags)},
		{Name: "PKG_CONFIG", Value: b.PkgconfigCmd()},

	CGO_CFLAGS_DISALLOW
		A regular expression specifying flags that must be disallowed
		from appearing in #cgo CFLAGS source code directives.
		Does not apply to the CGO_CFLAGS environment variable.
	CGO_CPPFLAGS, CGO_CPPFLAGS_ALLOW, CGO_CPPFLAGS_DISALLOW
		Like CGO_CFLAGS, CGO_CFLAGS_ALLOW, and CGO_CFLAGS_DISALLOW,
		but for the C preprocessor.
	CGO_CXXFLAGS, CGO_CXXFLAGS_ALLOW, CGO_CXXFLAGS_DISALLOW

permitted, notably alphanumeric characters and a few symbols, such as
'.', that will not be interpreted in unexpected ways. Attempts to use
forbidden characters will get a "malformed #cgo argument" error.

When building, the CGO_CFLAGS, CGO_CPPFLAGS, CGO_CXXFLAGS, CGO_FFLAGS and
CGO_LDFLAGS environment variables are added to the flags derived from
these directives. Package-specific flags should be set using the
directives, not the environment variables, so that builds work in