std.Target: Add Os.HurdVersionRange for Os.Tag.hurd.

This is necessary since isGnuLibC() is true for hurd, so we need to be able to
represent a glibc version for it.

Also add an Os.TaggedVersionRange.gnuLibCVersion() convenience function.

test/link/glibc_compat/build.zig

@@ -5,10 +5,7 @@ const builtin = @import("builtin");
 // run-time glibc version needs to be new enough.  Check the host's glibc
 // version.  Note that this does not allow for translation/vm/emulation
 // services to run these tests.
-const running_glibc_ver: ?std.SemanticVersion = switch (builtin.os.tag) {
-    .linux => builtin.os.version_range.linux.glibc,
-    else => null,
-};
+const running_glibc_ver = builtin.os.versionRange().gnuLibCVersion();
 
 pub fn build(b: *std.Build) void {
     const test_step = b.step("test", "Test");

test/link/glibc_compat/glibc_runtime_check.zig

@@ -21,7 +21,7 @@ const c_string = @cImport(
 );
 
 // Version of glibc this test is being built to run against
-const glibc_ver = builtin.target.os.version_range.linux.glibc;
+const glibc_ver = builtin.os.versionRange().gnuLibCVersion().?;
 
 // PR #17034 - fstat moved between libc_nonshared and libc
 fn checkStat() !void {