Add an env var to override make parallelism in ruby build (#28250)

* Add an env var to override make parallelism in ruby build

* add logging

src/ruby/ext/grpc/extconf.rb

@@ -70,8 +70,15 @@ unless windows
   puts 'Building internal gRPC into ' + grpc_lib_dir
   nproc = 4
   nproc = Etc.nprocessors * 2 if Etc.respond_to? :nprocessors
+  nproc_override = ENV['GRPC_RUBY_BUILD_PROCS']
+  unless nproc_override.nil? or nproc_override.size == 0
+    nproc = nproc_override
+    puts "Overriding make parallelism to #{nproc}"
+  end
   make = bsd ? 'gmake' : 'make'
-  system("#{make} -j#{nproc} -C #{grpc_root} #{grpc_lib_dir}/libgrpc.a CONFIG=#{grpc_config} Q=")
+  cmd = "#{make} -j#{nproc} -C #{grpc_root} #{grpc_lib_dir}/libgrpc.a CONFIG=#{grpc_config} Q="
+  puts "Building grpc native library: #{cmd}"
+  system(cmd)
   exit 1 unless $? == 0
 end
 

templates/src/ruby/ext/grpc/extconf.rb.template

@@ -72,8 +72,15 @@
     puts 'Building internal gRPC into ' + grpc_lib_dir
     nproc = 4
     nproc = Etc.nprocessors * 2 if Etc.respond_to? :nprocessors
+    nproc_override = ENV['GRPC_RUBY_BUILD_PROCS']
+    unless nproc_override.nil? or nproc_override.size == 0
+      nproc = nproc_override
+      puts "Overriding make parallelism to #{nproc}"
+    end
     make = bsd ? 'gmake' : 'make'
-    system("#{make} -j#{nproc} -C #{grpc_root} #{grpc_lib_dir}/libgrpc.a CONFIG=#{grpc_config} Q=")
+    cmd = "#{make} -j#{nproc} -C #{grpc_root} #{grpc_lib_dir}/libgrpc.a CONFIG=#{grpc_config} Q="
+    puts "Building grpc native library: #{cmd}"
+    system(cmd)
     exit 1 unless $? == 0
   end