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, 2 insertions, 0 deletions

diff --git a/src/error.cpp b/src/error.cpp
index 730c6e7193..2e92a98217 100644
--- a/src/error.cpp
+++ b/src/error.cpp
@@ -81,6 +81,8 @@ const char *err_str(Error err) {
         case ErrorWindowsSdkNotFound: return "Windows SDK not found";
         case ErrorUnknownDynamicLinkerPath: return "unknown dynamic linker path";
         case ErrorTargetHasNoDynamicLinker: return "target has no dynamic linker";
+        case ErrorInvalidAbiVersion: return "invalid C ABI version";
+        case ErrorInvalidOperatingSystemVersion: return "invalid operating system version";
     }
     return "(invalid error)";
 }