feat: Added SYSTEM flag support to fetch-content

docs/cmake-toml.md

@@ -151,6 +151,7 @@ condition = "mycondition"
 git = "https://github.com/myuser/gitcontent"
 tag = "v0.1"
 shallow = false
+system = false
 
 [fetch-content.svncontent]
 condition = "mycondition"

include/project_parser.hpp

@@ -155,6 +155,7 @@ struct Content {
     Condition<std::string> cmake_after;
     ConditionVector include_before;
     ConditionVector include_after;
+    bool system;
 };
 
 enum MsvcRuntimeType {

src/cmake_generator.cpp

@@ -917,7 +917,11 @@ void generate_cmake(const char *path, const parser::Project *parent_project) {
                 version_info = " (" + content.arguments.at("SVN_REVISION") + ")";
             }
             cmd("message")("STATUS", "Fetching " + content.name + version_info + "...");
-            cmd("FetchContent_Declare")(content.name, content.arguments);
+            if (content.system) {
+                cmd("FetchContent_Declare")(content.name, "SYSTEM", content.arguments);
+            } else {
+                cmd("FetchContent_Declare")(content.name, content.arguments);
+            }
             cmd("FetchContent_MakeAvailable")(content.name).endl();
 
             gen.conditional_includes(content.include_after);

src/project_parser.cpp

@@ -443,6 +443,15 @@ Project::Project(const Project *parent, const std::string &path, bool build) : p
             c.optional("cmake-after", content.cmake_after);
             c.optional("include-before", content.include_before);
             c.optional("include-after", content.include_after);
+            c.optional("system", content.system);
+
+            // Check if the minimum version requirement is satisfied (CMake 3.25)
+            if (c.contains("system") && !this->cmake_minimum_version(3, 25)) {
+                throw_key_error("The system argument is only supported on CMake version 3.25 and above.\nSet the CMake version in cmake.toml:\n"
+                                "[cmake]\n"
+                                "version = \"3.25\"\n",
+                                "system", "");
+            }
 
             for (const auto &argItr : itr.second.as_table()) {
                 std::string value;