[libc] Add missing LibcFPTestHelpers library

Differential Revision: https://reviews.llvm.org/D87690
diff --git a/libc/utils/MPFRWrapper/CMakeLists.txt b/libc/utils/MPFRWrapper/CMakeLists.txt
index 6a3c24e..cc66d1c 100644
--- a/libc/utils/MPFRWrapper/CMakeLists.txt
+++ b/libc/utils/MPFRWrapper/CMakeLists.txt
@@ -13,7 +13,7 @@
     MPFRUtils.h
   )
   add_dependencies(libcMPFRWrapper libc.utils.CPP.standalone_cpp libc.utils.FPUtil.fputil LibcUnitTest LLVMSupport)
-  target_link_libraries(libcMPFRWrapper -lmpfr -lgmp LibcUnitTest LLVMSupport)
+  target_link_libraries(libcMPFRWrapper -lmpfr -lgmp LibcFPTestHelpers LibcUnitTest LLVMSupport)
 else()
   message(WARNING "Math tests using MPFR will be skipped.")
 endif()