Limit calls to strip.sh on darwin

strip.sh can use a file descriptor per .o file when run on .a files,
which can hit the system file descriptor limit on darwin.  This
causes failures when manay variants of libgcc_stripped are built
simultaneously.  Put all strip rules on darwin into a pool that
limits them to 10 concurrent processes, which will limit the file
descriptor usage to ~7500.

Fixes: 132822437
Test: no mention of darwinStripPool in out/soong/build.ninja on linux
Test: m libgcc_stripped on darwin
Change-Id: I3d4fbbd8d44d2e9059a79df113ab95336ec2c658

cc/builder.go

@@ -123,12 +123,25 @@ var (
 	_ = pctx.SourcePathVariable("stripPath", "build/soong/scripts/strip.sh")
 	_ = pctx.SourcePathVariable("xzCmd", "prebuilts/build-tools/${config.HostPrebuiltTag}/bin/xz")
 
+	// b/132822437: objcopy uses a file descriptor per .o file when called on .a files, which runs the system out of
+	// file descriptors on darwin.  Limit concurrent calls to 10 on darwin.
+	darwinStripPool = func() blueprint.Pool {
+		if runtime.GOOS == "darwin" {
+			return pctx.StaticPool("darwinStripPool", blueprint.PoolParams{
+				Depth: 10,
+			})
+		} else {
+			return nil
+		}
+	}()
+
 	strip = pctx.AndroidStaticRule("strip",
 		blueprint.RuleParams{
 			Depfile:     "${out}.d",
 			Deps:        blueprint.DepsGCC,
 			Command:     "CROSS_COMPILE=$crossCompile XZ=$xzCmd CLANG_BIN=${config.ClangBin} $stripPath ${args} -i ${in} -o ${out} -d ${out}.d",
 			CommandDeps: []string{"$stripPath", "$xzCmd"},
+			Pool:        darwinStripPool,
 		},
 		"args", "crossCompile")