Revert "disable flaky incremental compilation tests"

This reverts commit 133abde but keeps
the tests disabled for the wasm target, which is the only configuration
that seems to fail, even though the error looks like a frontend error.

Author: jacobly0

test/incremental/add_decl

@@ -0,0 +1,62 @@
+#target=x86_64-linux-selfhosted
+#target=x86_64-linux-cbe
+#target=x86_64-windows-cbe
+//#target=wasm32-wasi-selfhosted
+#update=initial version
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(foo);
+}
+const foo = "good morning\n";
+#expect_stdout="good morning\n"
+
+#update=add new declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(foo);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_stdout="good morning\n"
+
+#update=reference new declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(bar);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_stdout="good evening\n"
+
+#update=reference missing declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(qux);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_error=ignored
+
+#update=add missing declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(qux);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+const qux = "good night\n";
+#expect_stdout="good night\n"
+
+#update=remove unused declarations
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(qux);
+}
+const qux = "good night\n";
+#expect_stdout="good night\n"

test/incremental/add_decl_namespaced

@@ -0,0 +1,62 @@
+#target=x86_64-linux-selfhosted
+#target=x86_64-linux-cbe
+#target=x86_64-windows-cbe
+//#target=wasm32-wasi-selfhosted
+#update=initial version
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().foo);
+}
+const foo = "good morning\n";
+#expect_stdout="good morning\n"
+
+#update=add new declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().foo);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_stdout="good morning\n"
+
+#update=reference new declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().bar);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_stdout="good evening\n"
+
+#update=reference missing declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().qux);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+#expect_error=ignored
+
+#update=add missing declaration
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().qux);
+}
+const foo = "good morning\n";
+const bar = "good evening\n";
+const qux = "good night\n";
+#expect_stdout="good night\n"
+
+#update=remove unused declarations
+#file=main.zig
+const std = @import("std");
+pub fn main() !void {
+    try std.io.getStdOut().writeAll(@This().qux);
+}
+const qux = "good night\n";
+#expect_stdout="good night\n"