[icu] Enable parallel builds (#6695)

* Add VCPKG_NUM_LOGICAL_CORES

* break out logic that retries running a command several times into its own function

* Parallelize icu

2 files changed, 23 insertions, 0 deletions

diff --git a/toolsrc/src/vcpkg/base/system.cpp b/toolsrc/src/vcpkg/base/system.cpp
index 48a701bfa..a11853524 100644
--- a/toolsrc/src/vcpkg/base/system.cpp
+++ b/toolsrc/src/vcpkg/base/system.cpp
@@ -596,6 +596,11 @@ namespace vcpkg
 #else
     void System::register_console_ctrl_handler() {}
 #endif
+
+    int System::get_num_logical_cores()
+    {
+        return std::thread::hardware_concurrency();
+    }
 }
 
 namespace vcpkg::Debug
diff --git a/toolsrc/src/vcpkg/build.cpp b/toolsrc/src/vcpkg/build.cpp
index 7bd6f467b..0a7c854b5 100644
--- a/toolsrc/src/vcpkg/build.cpp
+++ b/toolsrc/src/vcpkg/build.cpp
@@ -334,6 +334,23 @@ namespace vcpkg::Build
         return ret;

     }

 

+    static int get_concurrency()

+    {

+        static int concurrency = []{

+        auto user_defined_concurrency = System::get_environment_variable("VCPKG_MAX_CONCURRENCY");

+        if (user_defined_concurrency)

+        {

+            return std::stoi(user_defined_concurrency.value_or_exit(VCPKG_LINE_INFO));

+        }

+        else

+        {

+            return System::get_num_logical_cores() + 1;

+        }

+        }();

+

+        return concurrency;

+    }

+

     static ExtendedBuildResult do_build_package(const VcpkgPaths& paths,

                                                 const PreBuildInfo& pre_build_info,

                                                 const PackageSpec& spec,

@@ -372,6 +389,7 @@ namespace vcpkg::Build
             {"_VCPKG_DOWNLOAD_TOOL", to_string(config.build_package_options.download_tool)},

             {"FEATURES", Strings::join(";", config.feature_list)},

             {"ALL_FEATURES", all_features},

+            {"VCPKG_CONCURRENCY", std::to_string(get_concurrency())},

         };

 

         if (!System::get_environment_variable("VCPKG_FORCE_SYSTEM_BINARIES").has_value())