grpc: Update llvm-19 Konan dependency path after Kotlin compiler upgrade (#522)

Author: Jozott00

cinterop-c/README.md

@@ -3,8 +3,9 @@ It uses the Bazel build system and contains two libraries: protowire and kgrpc.
 
 ### Protowire
 
-Is a thin layer over the CodedStream implementation of the C++ protobuf library. 
-To build (e.g. ios_arm64) run 
+Is a thin layer over the CodedStream implementation of the C++ protobuf library.
+To build (e.g. ios_arm64) run
+
 ```bash
 bazel build :protowire_fat --config=ios_arm64 --config=release
 ```
@@ -15,9 +16,10 @@ We are using the gRPC-core library, which already exports its API with a C ABI.
 Therefore, the KgRPC library is almost empty primarily used for convenient functions
 or API that is not exposed by the C API.
 
-Because the gRPC takes a while to build when compiling for multiple targets, we store 
+Because the gRPC takes a while to build when compiling for multiple targets, we store
 it as a prebuilt static (fat) in `prebuilt-deps/grpc_fat`.
 The binary can be updated by running
+
 ```bash
 ./gradlew :grpc:grpc-core:buildDependencyCLibGrpc_fat_iosArm64
 ```
@@ -27,6 +29,32 @@ The binary can be updated by running
 To produce K/N compatible static libraries, we use the Konan toolchain for compilation.
 The Bazel toolchain is specified in `toolchain/` and requires the user to specify the
 `KONAN_HOME` variable like
+
 ```bash
 bazel build //:protowire --config=linux_arm64 --define=KONAN_HOME=$HOME/.konan/kotlin-native-prebuilt-macos-aarch64-2.2.10
-```
+```
+
+#### Upgrading the Kotlin Compiler Version
+
+When we upgrade the project's Kotlin compiler version, compilation for Linux will fail.
+Bazel will throw an error like
+
+```
+[1,351 / 1,353] Compiling src/kgrpc.cpp; 1s darwin-sandbox
+ERROR: /Users/jozott/development/jetbrains/kotlinx-rpc/cinterop-c/BUILD.bazel:11:11: Compiling src/kgrpc.cpp failed: absolute path inclusion(s) found in rule '//:kgrpc_lib':
+the source file 'src/kgrpc.cpp' includes the following non-builtin files with absolute paths (if these are builtin files, make sure these paths are in your toolchain):
+/Users/jozott/development/jetbrains/kotlinx-rpc/cinterop-c/BUILD.bazel:11:11: Compiling src/kgrpc.cpp failed: absolute path inclusion(s) found in rule '//:kgrpc_lib':
+
+/Users/jozott/.konan/dependencies/llvm-19-aarch64-macos-essentials-79/bin/clang ... -c src/kgrpc.cpp -o bazel-out/linux_arm64-opt/bin/_objs/kgrpc_lib/kgrpc.o
+  '/Users/jozott/.konan/dependencies/llvm-19-aarch64-macos-essentials-79/lib/clang/19/include/stdbool.h'
+  '/Users/jozott/.konan/dependencies/llvm-19-aarch64-macos-essentials-79/lib/clang/19/include/stdint.h'
+  ...
+```
+
+To fix this, we need to adjust the clang built-in include paths defined in the `toolchain/cc_toolchain_config.bzl` file.
+In the case above, the path at `cxx_builtin_include_directories` must be replaced by   
+`deps + "llvm-19-aarch64-macos-essentials-79/lib/clang/19/include"`.
+This must be done for aarch64 and x86_64 separately.
+The current LLVM toolchain bundle paths can be found in
+[kotlin/kotlin-native/gradle.properties](https://github.com/JetBrains/kotlin/blob/master/kotlin-native/gradle.properties)
+of the Kotlin repository.

cinterop-c/toolchain/cc_toolchain_config.bzl

@@ -193,7 +193,14 @@ def _impl(ctx):
         tool_paths = tool_paths,
         features = features,
         cxx_builtin_include_directories = [
+            # Built-in include directories from the toolchain.
+            # Only one will be available on the host (x64 or arm64).
+            # These paths must be updated after each upgrade of the project's Kotlin compiler version.
+            # After upgrading the Kotlin compiler, the C compiler will throw an error that certain includes are not
+            # are not part of the built-in include paths. In this case, replace the below path with the printed one.
+            # See the cinterop-c/README.md for more details.
             deps + "/llvm-19-aarch64-macos-essentials-75/lib/clang/19/include",
+            deps + "/llvm-19-x86_64-macos-essentials-103/lib/clang/19/include",
         ] + includes,
     )