src/glibc: Only support glibc v2.17 and later as linking targets

Earlier glibc's do not contain symbols (e.g., getauxval()) used by the Zig
standard library.

Filter the list shown by Zig targets, too:

  $ zig targets | jq -c '.glibc'
  ["2.17.0","2.18.0","2.19.0","2.20.0","2.21.0","2.22.0","2.23.0","2.24.0","2.25.0","2.26.0","2.27.0","2.28.0","2.29.0","2.30.0","2.31.0","2.32.0","2.33.0","2.34.0","2.35.0","2.36.0","2.37.0","2.38.0"]

Fixes #17769

src/glibc.zig

@@ -20,7 +20,7 @@ pub const Lib = struct {
 };
 
 pub const ABI = struct {
-    all_versions: []const Version,
+    all_versions: []const Version, // all defined versions (one abilist from v2.0.0 up to current)
     all_targets: []const target_util.ArchOsAbi,
     /// The bytes from the file verbatim, starting from the u16 number
     /// of function inclusions.
@@ -741,6 +741,11 @@ pub fn buildSharedObjects(comp: *Compilation, prog_node: *std.Progress.Node) !vo
         break :blk latest_index;
     };
 
+    if (!isSupportedGlibcVersion(target_version)) { // only a subset of all_versions are supported
+        log.warn("Unsupported target glibc version: {}", .{target_version});
+        return error.InvalidTargetGLibCVersion;
+    }
+
     {
         var map_contents = std.ArrayList(u8).init(arena);
         for (metadata.all_versions[0 .. target_ver_index + 1]) |ver| {
@@ -1131,3 +1136,9 @@ pub fn needsCrtiCrtn(target: std.Target) bool {
         else => true,
     };
 }
+
+// Glibc v2.17 is the oldest supported linking target due to dependencies
+// from the Zig standard library.
+pub fn isSupportedGlibcVersion(ver: Version) bool {
+    return (ver.major > 2) or ((ver.major == 2) and (ver.minor >= 17));
+}

src/print_targets.zig

@@ -79,9 +79,11 @@ pub fn cmdTargets(
     try jws.objectField("glibc");
     try jws.beginArray();
     for (glibc_abi.all_versions) |ver| {
-        const tmp = try std.fmt.allocPrint(allocator, "{}", .{ver});
-        defer allocator.free(tmp);
-        try jws.write(tmp);
+        if (glibc.isSupportedGlibcVersion(ver)) {
+            const tmp = try std.fmt.allocPrint(allocator, "{}", .{ver});
+            defer allocator.free(tmp);
+            try jws.write(tmp);
+        }
     }
     try jws.endArray();