A continuation of previous fix for malloc hooks which got removed
from the new glibc library.
The pre-compiled jemalloc has definitions which interpose hooks
in glibc leading to linking errors with multiple hook definitions.
A simple fix is to skip doing the workaround when using jemalloc
from pre-compiled libraries.
This will likely be revisited in the future, but for now it is
important to fix compilation errors for developers.
cca416cfe6