Run multiple gbc jobs when using Bond.CSharp.targets

By default the Bond.CSharp.targets will run 2 fewer concurrent jobs than
there are processor cores on the machine. User can override this
behaviour for their project by specifying a different `--jobs` option in
`BondOptions` property.

cs/build/Bond.CSharp.targets

@@ -69,7 +69,7 @@
       <_BondExe Condition="'$(OS)' != 'Unix' Or Exists('$(BOND_COMPILER_PATH)\gbc.exe')">"$(BOND_COMPILER_PATH)\gbc.exe"</_BondExe>
       <_BondExe Condition="'$(OS)' == 'Unix' And !Exists('$(BOND_COMPILER_PATH)\gbc.exe')">gbc</_BondExe>
       <_BondImportDirs>--import-dir="$(BOND_INCLUDE_PATH)" @(BondImportDirectory -> '--import-dir=&quot;%(Identity)\.&quot;',' ')</_BondImportDirs>
-      <_BondCommand>$(_BondExe) $(BondCodegenMode) $(_BondImportDirs) --namespace=bond=Bond --output-dir="$(BondOutputDirectory)\."</_BondCommand>
+      <_BondCommand>$(_BondExe) $(BondCodegenMode) $(_BondImportDirs) --jobs=-2 --namespace=bond=Bond --output-dir="$(BondOutputDirectory)\."</_BondCommand>
     </PropertyGroup>
 
     <!-- We'll optimize to generate in a single command where possible -->

cs/nuget/readme.txt

@@ -28,6 +28,11 @@ properties/items in your project:
     $BondOptions         : Additional options to pass to the gbc compiler for this project
     $BondCodegenMode     : Code generation mode for gbc to use (default c#)
 
+By default gbc is executed with `--jobs=-2` option to compile multiple .bond
+files concurrently, using 2 fewer jobs than there are processor cores. You can
+override this behaviour by setting a different value for `--jobs` option via
+the `BondOptions` property.
+
 For details see http://microsoft.github.io/bond/manual/bond_cs.html#code-generation
 
 ReSharper