introduce operating system version ranges as part of the target

 * re-introduce `std.build.Target` which is distinct from `std.Target`.
   `std.build.Target` wraps `std.Target` so that it can be annotated as
   "the native target" or an explicitly specified target.
 * `std.Target.Os` is moved to `std.Target.Os.Tag`. The former is now a
   struct which has the tag as well as version range information.
 * `std.elf` gains some more ELF header constants.
 * `std.Target.parse` gains the ability to parse operating system
   version ranges as well as glibc version.
 * Added `std.Target.isGnuLibC()`.
 * self-hosted dynamic linker detection and glibc version detection.
   This also adds the improved logic using `/usr/bin/env` rather than
   invoking the system C compiler to find the dynamic linker when zig
   is statically linked. Related: #2084
   Note: this `/usr/bin/env` code is work-in-progress.
 * `-target-glibc` CLI option is removed in favor of the new `-target`
   syntax. Example: `-target x86_64-linux-gnu.2.27`

closes #1907

1 files changed, 1 insertions, 1 deletions

diff --git a/lib/std/os/linux.zig b/lib/std/os/linux.zig
index d11f206482..30dba85e51 100644
--- a/lib/std/os/linux.zig
+++ b/lib/std/os/linux.zig
@@ -1070,7 +1070,7 @@ pub fn tcsetattr(fd: fd_t, optional_action: TCSA, termios_p: *const termios) usi
 }
 
 test "" {
-    if (builtin.os == .linux) {
+    if (builtin.os.tag == .linux) {
         _ = @import("linux/test.zig");
     }
 }