Added simple swiftpm package file with module map and empty C file to trick the compiler to build the empty C target.

Author: smumriak

Package.swift

@@ -0,0 +1,45 @@
+// swift-tools-version:5.2
+
+import PackageDescription
+
+let package = Package(
+    name: "cglm",
+    products: [
+        .library(name: "cglm", type: .static, targets: ["cglmHeader"]),
+        .library(name: "cglmc", targets: ["cglmCompiled"]),
+    ],
+    dependencies: [],
+    targets: [
+        .target(
+            name: "cglmCompiled",
+            path: "./",
+            exclude: [
+                "./docs",
+                "./dummySrcForSwift",
+                "./include",
+                "./test",
+                "./win",
+            ],
+            sources: [
+                "./src",
+            ],
+            publicHeadersPath: "./include"
+        ),
+        .target(
+            name: "cglmHeader",
+            path: "./",
+            exclude: [
+                "./docs",
+                "./include",
+                "./src",
+                "./test",
+                "./win",
+            ],
+            sources: [
+                "./dummySrcForSwift",
+            ],
+            publicHeadersPath: "./include"
+        ),
+    ],
+    cLanguageStandard: .c11
+)

dummySrcForSwift/empty.c

@@ -0,0 +1,14 @@
+module cglm {
+    header "cglm/cglm.h"
+    header "cglm/struct.h"
+    
+    export *
+}
+
+module cglmc {
+    header "cglm/cglm.h"
+    header "cglm/struct.h"
+    header "cglm/call.h"
+    
+    export *
+}