Add standalone test for common symbols

test/standalone.zig

@@ -15,6 +15,7 @@ pub fn addCases(cases: *tests.StandaloneContext) void {
     cases.addBuildFile("test/standalone/static_c_lib/build.zig", .{});
     cases.addBuildFile("test/standalone/link_interdependent_static_c_libs/build.zig", .{});
     cases.addBuildFile("test/standalone/link_static_lib_as_system_lib/build.zig", .{});
+    cases.addBuildFile("test/standalone/link_common_symbols/build.zig", .{});
     cases.addBuildFile("test/standalone/issue_339/build.zig", .{});
     cases.addBuildFile("test/standalone/issue_8550/build.zig", .{});
     cases.addBuildFile("test/standalone/issue_794/build.zig", .{});

test/standalone/link_common_symbols/a.c

@@ -0,0 +1,6 @@
+int i;
+int j;
+
+int add_to_i_and_j(int x) {
+  return x + i + j;
+}

test/standalone/link_common_symbols/b.c

@@ -0,0 +1,6 @@
+long i;
+int j = 2;
+
+void incr_i() {
+  i++;
+}

test/standalone/link_common_symbols/build.zig

@@ -0,0 +1,16 @@
+const Builder = @import("std").build.Builder;
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+
+    const lib_a = b.addStaticLibrary("a", null);
+    lib_a.addCSourceFiles(&.{ "a.c", "b.c" }, &.{"-fcommon"});
+    lib_a.setBuildMode(mode);
+
+    const test_exe = b.addTest("main.zig");
+    test_exe.setBuildMode(mode);
+    test_exe.linkLibrary(lib_a);
+
+    const test_step = b.step("test", "Test it");
+    test_step.dependOn(&test_exe.step);
+}

test/standalone/link_common_symbols/main.zig

@@ -0,0 +1,11 @@
+const std = @import("std");
+const expect = std.testing.expect;
+
+extern fn incr_i() void;
+extern fn add_to_i_and_j(x: c_int) c_int;
+
+test "import C common symbols" {
+    incr_i();
+    const res = add_to_i_and_j(2);
+    try expect(res == 5);
+}