fix FindDoubleConversion.cmake to work properly

Summary:
The code in `FindDoubleConversion.cmake` called
`FIND_PACKAGE_HANDLE_STANDARD_ARGS()` with the wrong arguments.  The first
argument must match the package name: since this file is called
`FindDoubleConversion` the first argument must be `DoubleConversion`.

Previously this code was passing in `DOUBLE_CONVERSION`, causing it to set
`DOUBLE_CONVERSION_FOUND` instead of `DoubleConversion_FOUND`.  Since this
module did not set `DoubleConversion_FOUND` the `find_package()` call assumed
it always succeeded, even when the double-conversion library was not found.

Also remove the extra status message.  `FIND_PACKAGE_HANDLE_STANDARD_ARGS()`
already prints out a status message as long as `find_package()` was called
without the `QUIET` argument.

Reviewed By: yfeldblum

Differential Revision: D23588980

fbshipit-source-id: 8c088930b1b01c027403c3e425f1924f6149f72a

CMake/FindDoubleConversion.cmake

@@ -23,14 +23,9 @@ find_path(DOUBLE_CONVERSION_INCLUDE_DIR double-conversion/double-conversion.h)
 find_library(DOUBLE_CONVERSION_LIBRARY NAMES double-conversion)
 
 include(FindPackageHandleStandardArgs)
-FIND_PACKAGE_HANDLE_STANDARD_ARGS(
-    DOUBLE_CONVERSION DEFAULT_MSG
-    DOUBLE_CONVERSION_LIBRARY DOUBLE_CONVERSION_INCLUDE_DIR)
-
-if (NOT DOUBLE_CONVERSION_FOUND)
-  message(STATUS "Using third-party bundled double-conversion")
-else()
-  message(STATUS "Found double-conversion: ${DOUBLE_CONVERSION_LIBRARY}")
-endif (NOT DOUBLE_CONVERSION_FOUND)
+find_package_handle_standard_args(
+  DoubleConversion
+  DEFAULT_MSG
+  DOUBLE_CONVERSION_LIBRARY DOUBLE_CONVERSION_INCLUDE_DIR)
 
 mark_as_advanced(DOUBLE_CONVERSION_INCLUDE_DIR DOUBLE_CONVERSION_LIBRARY)