Add documentation of how to configure SourceKit-LSP for embedded projects

Author: ahoppen

Documentation/README.md

@@ -7,3 +7,4 @@ The following documentation documents are intended for users of SourceKit-LSP.
 - [Editor Integration](Editor%20Integration.md)
 - [Enable Experimental Background Indexing](Enable%20Experimental%20Background%20Indexing.md)
 - [Environment Variables](Environment%20Variables.md)
+- [Using SourceKit-LSP with Embedded Projects](Using%20SourceKit-LSP%20with%20Embedded%20Projects.md)

Documentation/Using SourceKit-LSP with Embedded Projects.md

@@ -0,0 +1,26 @@
+# Using SourceKit-LSP with Embedded Projects
+
+If you need to pass additional options in the `swift build` invocation to build your project, SourceKit-LSP needs to know about these as well to fully understand your project. To tell SourceKit-LSP about these options, add a `.sourcekit-lsp/config.json` file to your project’s root folder and add the arguments you pass to `swift build` to that configuration file as described [here](Configuration%20File.md).
+
+For example, if you use the following invocation to build your project
+
+```sh
+swift build \
+  --configuration release \
+  --triple armv7em-apple-none-macho \
+  -Xcc -D__APPLE__ -Xcc -D__MACH__ \
+  -Xswiftc -Xfrontend -Xswiftc -disable-stack-protector
+```
+
+Then the `.sourcekit-lsp/config.json` file should contain
+
+```json
+{
+  "swiftPM": {
+    "configuration": "release",
+    "triple": "armv7em-apple-none-macho",
+    "cCompilerFlags": ["-D__APPLE__", "-D__MACH__"],
+    "swiftCompilerFlags": ["-Xfrontend", "-disable-stack-protector"]
+  }
+}
+```

README.md

@@ -11,6 +11,9 @@ https://www.swift.org/tools has a list of popular editors that support LSP and c
 
 To learn more about SourceKit-LSP, refer to the [Documentation](Documentation).
 
+> [!NOTE]
+> If you are using SourceKit-LSP with a SwiftPM project in which you need to pass additional arguments to the `swift build` invocation, as is commonly the case for embedded projects, you need to teach SourceKit-LSP about those arguments as described in [Using SourceKit-LSP with Embedded Projects](Documentation/Using%20SourceKit-LSP%20with%20Embedded%20Projects.md).
+
 ## Reporting Issues
 
 If you should hit any issues while using SourceKit-LSP, we appreciate bug reports on [GitHub Issue](https://github.com/swiftlang/sourcekit-lsp/issues/new/choose).