build system: consolidate duplicate code and more

 * add ability to add assembly files when building an exe, obj, or lib
 * add implicit cast from `[N]T` to `?[]const T` (closes #343)
 * remove link_exe and link_lib in favor of allowing build_exe and
   build_lib support no root zig source file

2 files changed, 13 insertions, 6 deletions

diff --git a/test/cases/cast.zig b/test/cases/cast.zig
index f6425ee464..a9c7b068a4 100644
--- a/test/cases/cast.zig
+++ b/test/cases/cast.zig
@@ -150,3 +150,12 @@ fn peerTypeEmptyArrayAndSlice(a: bool, slice: []const u8) -> []const u8 {
 
     return slice[0...1];
 }
+
+test "implicitly cast from [N]T to ?[]const T" {
+    assert(mem.eql(u8, ??castToMaybeSlice(), "hi"));
+    comptime assert(mem.eql(u8, ??castToMaybeSlice(), "hi"));
+}
+
+fn castToMaybeSlice() -> ?[]const u8 {
+    return "hi";
+}
diff --git a/test/tests.zig b/test/tests.zig
index d115ed037a..b89a47eff7 100644
--- a/test/tests.zig
+++ b/test/tests.zig
@@ -355,18 +355,16 @@ pub const CompareOutputContext = struct {
                         return;
                 }
 
-                const assembly = b.addAssemble("test", root_src);
+                const exe = b.addExecutable("test", null);
+                exe.addAssemblyFile(root_src);
+                exe.setOutputPath(exe_path);
 
                 for (case.sources.toSliceConst()) |src_file| {
                     const expanded_src_path = %%os.path.join(b.allocator, "test_artifacts", src_file.filename);
                     const write_src = b.addWriteFile(expanded_src_path, src_file.source);
-                    assembly.step.dependOn(&write_src.step);
+                    exe.step.dependOn(&write_src.step);
                 }
 
-                const exe = b.addLinkExecutable("test");
-                exe.addAssembly(assembly);
-                exe.setOutputPath(exe_path);
-
                 const run_and_cmp_output = RunCompareOutputStep.create(self, exe_path, annotated_case_name,
                     case.expected_output);
                 run_and_cmp_output.step.dependOn(&exe.step);