Don't install static libraries if they're not requested.

https://crbug.com/906078

--- a/cmake/modules/AddLLVM.cmake
+++ b/cmake/modules/AddLLVM.cmake
@@ -639,10 +639,12 @@
         set_property(GLOBAL PROPERTY LLVM_HAS_EXPORTS True)
       endif()
 
-      install(TARGETS ${name}
-              ${export_to_llvmexports}
-              ${install_type} DESTINATION ${install_dir}
-              COMPONENT ${name})
+      if(ARG_SHARED OR NOT LLVM_BUILD_LLVM_DYLIB)
+        install(TARGETS ${name}
+                ${export_to_llvmexports}
+                ${install_type} DESTINATION ${install_dir}
+                COMPONENT ${name})
+      endif()
 
       if (NOT CMAKE_CONFIGURATION_TYPES)
         add_llvm_install_targets(install-${name}