ProgramFiles is not available under Linux, nor is NSIS compiler

ccnet.build

@@ -31,7 +31,7 @@
     <property name="gendarme.executable"	readonly="true"		value="${path::combine( path::combine(tools.dir, 'Gendarme'), 'gendarme.exe')}" />
     <property name="ndepend.executable"		readonly="true"		value="${path::combine( path::combine(tools.dir, 'NDepend'), 'NDepend.Console.exe')}" />
     <property name="fxcop.executable"		readonly="true"		value="${path::combine( path::combine(tools.dir, 'FxCop'), 'FxCopCmd.exe')}" />
-    <property name="nsis.executable"		readonly="true"		value="${path::combine( path::combine(environment::get-variable('ProgramFiles(x86)'), 'NSIS'), 'makensis.exe')}" />
+    <property name="nsis.executable"		readonly="true"		value="${path::combine( path::combine(environment::get-variable('ProgramFiles(x86)'), 'NSIS'), 'makensis.exe')}" if="${environment::variable-exists('ProgramFiles(x86)')}"  />
     <!-- If NUGET_EXE env. variable does not exist, fallback to the one provided by Cake -->
     <property name="nuget.executable"		            		value="${environment::get-variable('NUGET_EXE')}" if="${environment::variable-exists('NUGET_EXE')}" />
     <property name="nuget.executable"		            	    value="${path::combine( path::combine(tools.dir, 'Cake'), 'nuget.exe')}" if="${not environment::variable-exists('NUGET_EXE')}"  />