[6.2] FreeBSD: Build failure -- error: cannot find '__GLIBC__' in scope

[etcwilde]

Description

Swift-Testing fails to build on FreeBSD due to usage of unguarded GNU extensions.
FreeBSD, OpenBSD, and everything Unix-y that isn't Android or Apple uses the glibc module map for importing the C library. This means that canImport(Glibc) is not sufficient for guarding GNU extensions.

/home/ewilde/Work/Swift-Project/swift-testing/Sources/Testing/Support/Versions.swift:163:29: error: cannot find '__GLIBC__' in scope
161 |   // Default to the statically available version number if the function call
162 |   // fails for some reason.
163 |   var major = Int(clamping: __GLIBC__)
    |                             `- error: cannot find '__GLIBC__' in scope
164 |   var minor = Int(clamping: __GLIBC_MINOR__)
165 | 

/home/ewilde/Work/Swift-Project/swift-testing/Sources/Testing/Support/Versions.swift:164:29: error: cannot find '__GLIBC_MINOR__' in scope
162 |   // fails for some reason.
163 |   var major = Int(clamping: __GLIBC__)
164 |   var minor = Int(clamping: __GLIBC_MINOR__)
    |                             `- error: cannot find '__GLIBC_MINOR__' in scope
165 | 
166 |   if let strVersion = gnu_get_libc_version() {

/home/ewilde/Work/Swift-Project/swift-testing/Sources/Testing/Support/Versions.swift:166:23: error: cannot find 'gnu_get_libc_version' in scope
164 |   var minor = Int(clamping: __GLIBC_MINOR__)
165 | 
166 |   if let strVersion = gnu_get_libc_version() {
    |                       `- error: cannot find 'gnu_get_libc_version' in scope
167 |     withUnsafeMutablePointer(to: &major) { major in
168 |       withUnsafeMutablePointer(to: &minor) { minor in

Reproduction

swift build

Expected behavior

it builds

Environment

Swift-Testing checkout: c171888

FreeBSD 14.3-RELEASE FreeBSD 14.3-RELEASE releng/14.3-n271432-8c9ce319fef7 GENERIC arm64

Swift version 6.2-dev (LLVM 983d4c29b28d5cd, Swift 7460ce1c7230afc)
Target: aarch64-unknown-freebsd14.3

Additional information

No response