Add basic tests for the new builtins

test/compile_errors.zig

@@ -7504,4 +7504,22 @@ pub fn addCases(cases: *tests.CompileErrorContext) void {
     , &[_][]const u8{
         ":3:52: error: slice '[]const u8' cannot have its bytes reinterpreted",
     });
+
+    cases.add("wasmMemorySize is a compile error in non-Wasm targets",
+        \\export fn foo() void {
+        \\    _ = @wasmMemorySize();
+        \\    return;
+        \\}
+    , &[_][]const u8{
+        "tmp.zig:2:9: error: @wasmMemorySize is a wasm32 feature only",
+    });
+
+    cases.add("wasmMemoryGrow is a compile error in non-Wasm targets",
+        \\export fn foo() void {
+        \\    _ = @wasmMemoryGrow(1);
+        \\    return;
+        \\}
+    , &[_][]const u8{
+        "tmp.zig:2:9: error: @wasmMemoryGrow is a wasm32 feature only",
+    });
 }

test/stage1/behavior.zig

@@ -126,6 +126,9 @@ comptime {
     _ = @import("behavior/var_args.zig");
     _ = @import("behavior/vector.zig");
     _ = @import("behavior/void.zig");
+    if (builtin.arch == .wasm32) {
+        _ = @import("behavior/wasm.zig");
+    }
     _ = @import("behavior/while.zig");
     _ = @import("behavior/widening.zig");
 }

test/stage1/behavior/wasm.zig

@@ -0,0 +1,8 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
+test "memory size and grow" {
+    var prev = @wasmMemorySize();
+    expect(prev == @wasmMemoryGrow(1));
+    expect(prev + 1 == @wasmMemorySize());
+}