Export the INTERFACE_PIC property.

Source/cmExportInstallFileGenerator.cxx

@@ -89,6 +89,8 @@ bool cmExportInstallFileGenerator::GenerateMainFile(std::ostream& os)
                                   te,
                                   cmGeneratorExpression::InstallInterface,
                                   properties, missingTargets);
+    this->PopulateInterfaceProperty("INTERFACE_POSITION_INDEPENDENT_CODE",
+                                  te, properties);
 
     this->GenerateInterfaceProperties(te, os, properties);
     }