Add --no-as-needed linker flag for jemalloc

Summary:For reasons that remain unclear the ubuntu 14.04 and 15.10 builders have been
stripping the jemalloc dependency from their hhvm binaries at link time. The
resulting binaries will always segfault on start unless LD_PRELOAD includes
jemalloc. This flag prevents the linker from performing this strip.

Reviewed By: jasone, Orvid

Differential Revision: D3083799

fb-gh-sync-id: 9122e0f04753d1683373e31ba009ca0a5772d894
shipit-source-id: 9122e0f04753d1683373e31ba009ca0a5772d894

Author: paulbiss

CMake/HPHPSetup.cmake

@@ -126,6 +126,12 @@ include(HPHPCompiler)
 include(HPHPFunctions)
 include(HPHPFindLibs)
 
+# Ubuntu 15.10 and 14.04 have been failing to include a dependency on jemalloc
+# as a these linked flags force the dependency to be recorded
+if (JEMALLOC_ENABLED AND LINUX)
+  LIST(APPEND HHVM_LINK_LIBRARIES -Wl,--no-as-needed ${JEMALLOC_LIB} -Wl,--as-needed)
+endif()
+
 if (HHVM_VERSION_OVERRIDE)
   parse_version("HHVM_VERSION_" ${HHVM_VERSION_OVERRIDE})
   add_definitions("-DHHVM_VERSION_OVERRIDE")