tests: add `test-incremental` step

This is contained in the `test` step, so is tested by CI.

This commit also includes some enhancements to the `incr-check` tool to
make this work correctly.

1 files changed, 4 insertions, 0 deletions

diff --git a/build.zig b/build.zig
index 731b825c07..a5f4cd5675 100644
--- a/build.zig
+++ b/build.zig
@@ -577,6 +577,10 @@ pub fn build(b: *std.Build) !void {
     } else {
         update_mingw_step.dependOn(&b.addFail("The -Dmingw-src=... option is required for this step").step);
     }
+
+    const test_incremental_step = b.step("test-incremental", "Run the incremental compilation test cases");
+    try tests.addIncrementalTests(b, test_incremental_step);
+    test_step.dependOn(test_incremental_step);
 }
 
 fn addWasiUpdateStep(b: *std.Build, version: [:0]const u8) !void {