zld: permit system static libs

This commits permits passing in static archives using the system
lib flag `-la`. With this commit, `zig ld` will now look firstly for
a dynamic library (which always takes precedence), and will fall back
on `liba.a` if the dylib is not found. The static archive is searched
for in the system lib search dirs like the dylibs.

1 files changed, 6 insertions, 0 deletions

diff --git a/src/link/MachO/Object.zig b/src/link/MachO/Object.zig
index 4d2ade7aad..4160c2d75c 100644
--- a/src/link/MachO/Object.zig
+++ b/src/link/MachO/Object.zig
@@ -485,3 +485,9 @@ pub fn parseDataInCode(self: *Object) !void {
         try self.data_in_code_entries.append(self.allocator, dice);
     }
 }
+
+pub fn isObject(file: fs.File) !bool {
+    const header = try file.reader().readStruct(macho.mach_header_64);
+    try file.seekTo(0);
+    return header.filetype == macho.MH_OBJECT;
+}