cmake: Add options for parallel builds to --build mode

While we already support `cmake --build . -- -j`, the options after `--`
are specific to the native build tool.  Add new options `--parallel
[<N>]` and `-j [<N>]` to abstract this and map to the proper option
for the native build tool.

1 files changed, 26 insertions, 0 deletions

diff --git a/Source/cmGlobalJOMMakefileGenerator.cxx b/Source/cmGlobalJOMMakefileGenerator.cxx
index 18c45e0d86..0f41ea1482 100644
--- a/Source/cmGlobalJOMMakefileGenerator.cxx
+++ b/Source/cmGlobalJOMMakefileGenerator.cxx
@@ -52,3 +52,29 @@ void cmGlobalJOMMakefileGenerator::PrintCompilerAdvice(
   }
   this->cmGlobalUnixMakefileGenerator3::PrintCompilerAdvice(os, lang, envVar);
 }
+
+void cmGlobalJOMMakefileGenerator::GenerateBuildCommand(
+  std::vector<std::string>& makeCommand, const std::string& makeProgram,
+  const std::string& projectName, const std::string& projectDir,
+  const std::string& targetName, const std::string& config, bool fast,
+  int jobs, bool verbose, std::vector<std::string> const& makeOptions)
+{
+  std::vector<std::string> jomMakeOptions;
+
+  // Since we have full control over the invocation of JOM, let us
+  // make it quiet.
+  jomMakeOptions.push_back(this->MakeSilentFlag);
+  jomMakeOptions.insert(jomMakeOptions.end(), makeOptions.begin(),
+                        makeOptions.end());
+
+  // JOM does parallel builds by default, the -j is only needed if a specific
+  // number is given
+  // see https://github.com/qt-labs/jom/blob/v1.1.2/src/jomlib/options.cpp
+  if (jobs == cmake::DEFAULT_BUILD_PARALLEL_LEVEL) {
+    jobs = cmake::NO_BUILD_PARALLEL_LEVEL;
+  }
+
+  cmGlobalUnixMakefileGenerator3::GenerateBuildCommand(
+    makeCommand, makeProgram, projectName, projectDir, targetName, config,
+    fast, jobs, verbose, jomMakeOptions);
+}