cmake: fix "WITH_STATIC_LIBSTDCXX"

cmake: fix "WITH_STATIC_LIBSTDCXX"

- do not link libkv with ALLOC_LIBS, it turns out that if we link
tcmalloc *before* -static-libstdc++ -static-libgcc, libstdc++ and gcc
libs will show up in `ldd` output
- add `-static-libstdc++ -static-libgcc` to CMAKE_SHARED_LINKER_FLAGS
and CMAKE_EXE_LINKER_FLAGS instead of adding them to all shared
libraries and executable. simpler this way.
- link against libtcmalloc statically, because libtcmalloc is a C++
library, linking against it dynamically and linking against C++ runtime
statically will pull in depdencies on two versions of C++ runtime, which
will bring down the app at run-time.
- do not pass '-pie' to linker when building executable if
`WITH_STATIC_LIBSTDCXX` and tcmalloc is used, because the static tcmalloc
is not compiled with PIC.
- only apply '-pie' if ENABLE_SHARED is enabled.

Signed-off-by: Kefu Chai <kchai@redhat.com>