python3-grpcio(-tools): fix build concurrency issue

Set GRPC_PYTHON_BUILD_EXT_COMPILER_JOBS to limit spawned compiler
processes. Without this it uses all available CPUs (via
multiprocessing.cpu_count()) and can exhaust build host since there are
lot of files to compile (e.g. with 128 cores it manages to spawn 128 gcc
processes)

Note that this is a general problem for all setuptools based builds with
build_ext compilation which can either compile with 1 thread or
cpu_count threads. grpcio hot-patches setuptools and allows to set
specific build concurrency value.

Signed-off-by: Peter Marko <peter.marko@siemens.com>
Signed-off-by: Khem Raj <raj.khem@gmail.com>

meta-python/recipes-devtools/python/python3-grpcio_1.70.0.bb

@@ -29,6 +29,10 @@ export GRPC_PYTHON_BUILD_SYSTEM_OPENSSL = "1"
 export GRPC_PYTHON_BUILD_SYSTEM_RE2 = "1"
 export GRPC_PYTHON_BUILD_SYSTEM_ZLIB = "1"
 
+do_compile:prepend() {
+    export GRPC_PYTHON_BUILD_EXT_COMPILER_JOBS="${@oe.utils.parallel_make(d, False)}"
+}
+
 GRPC_CFLAGS ?= ""
 GRPC_CFLAGS:append:toolchain-clang = " -fvisibility=hidden -fno-wrapv -fno-exceptions"
 export GRPC_PYTHON_CFLAGS = "${GRPC_CFLAGS}"