$ gcc --version | head -1
gcc (GCC) 4.4.7 20120313 (Red Hat 4.4.7-4)
$ module show compilers/gcc/4.8.3
-------------------------------------------------------------------
/etc/modulefiles/compilers/gcc/4.8.3:

module-whatis    load GCC 4.8.3 environment 
module-whatis    Modifies: PATH, LD_LIBRARY_PATH, MANPATH 
prepend-path     PATH /projects/opt/gcc/4.8.3/bin 
prepend-path     LD_LIBRARY_PATH /projects/opt/gcc/4.8.3/lib64:/projects/opt/gcc/4.8.3/lib 
prepend-path     MANPATH /projects/opt/gcc/4.8.3/share/man 
setenv       CC gcc 
setenv       CXX g++ 
setenv       CPP cpp 
setenv       FC gfortran 
setenv       F77 gfortran 
setenv       F90 gfortran 
-------------------------------------------------------------------

$ module load compilers/gcc/4.8.3
$ gcc --version | head -1
gcc (GCC) 4.8.3
$ spack compilers
==> Available compilers
-- gcc ----------------------------------------------------------
[email protected]
$ spack compiler add
==> Added 1 new compiler to /home/pakin/.spackconfig
[email protected]
$ spack install libelf
==> Installing libelf
==> Trying to fetch from http://www.mr511.de/software/libelf-0.8.12.tar.gz
######################################################################## 100.0%
==> Staging archive: /home/pakin/spack/var/spack/stage/[email protected]%[email protected]=unknown_arch/libelf-0.8.12.tar.gz
==> Created stage in /home/pakin/spack/var/spack/stage/[email protected]%[email protected]=unknown_arch.
==> No patches needed for libelf.
==> Building libelf.
creating cache ./config.cache
checking whether make sets ${MAKE}... yes
checking for gcc... cc
checking whether the C compiler (cc  ) works... no
configure: error: installation or configuration problem: C compiler cannot create executables.
Traceback (most recent call last):
  File "/home/pakin/spack/lib/spack/spack/package.py", line 754, in do_install
self.install(self.spec, self.prefix)
  File "/home/pakin/spack/var/spack/packages/libelf/package.py", line 43, in install
"--disable-debug")
  File "/home/pakin/spack/lib/spack/spack/util/executable.py", line 83, in __call__
% (" ".join(cmd), proc.returncode))
spack.util.executable.ProcessError: command './configure --prefix=/home/pakin/spack/opt/unknown_arch/[email protected]/[email protected] --enable-shared --disable-dependency-tracking --disable-debug' returned error code 1
$ cat /tmp/spack-stage/spack-stage-J87_JC/libelf-0.8.12/config.log
This file contains any messages produced by compilers while
running configure, to aid debugging if configure makes a mistake.

configure:582: checking whether make sets ${MAKE}
configure:611: checking for gcc
configure:724: checking whether the C compiler (cc  ) works
configure:740: cc -o conftest    conftest.c  1>&5
/projects/opt/gcc/4.8.3/packages/gcc-4.8.3/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.8.3/cc1: error while loading shared libraries: libmpc.so.3: cannot open shared object file: No such file or directory
configure: failed program was:

#line 735 "configure"
#include "confdefs.h"

main(){return(0);}
$ ldd /projects/opt/gcc/4.8.3/packages/gcc-4.8.3/bin/../libexec/gcc/x86_64-unknown-linux-gnu/4.8.3/cc1
    linux-vdso.so.1 =>  (0x00007fff5b9ff000)
    libmpc.so.3 => /projects/opt/gcc/4.8.3/lib/libmpc.so.3 (0x00002ad3b51d7000)
    libmpfr.so.4 => /projects/opt/gcc/4.8.3/lib/libmpfr.so.4 (0x00002ad3b53ef000)
    libgmp.so.10 => /projects/opt/gcc/4.8.3/lib/libgmp.so.10 (0x00002ad3b564b000)
    libdl.so.2 => /lib64/libdl.so.2 (0x0000003167000000)
    libz.so.1 => /lib64/libz.so.1 (0x0000003167400000)
    libstdc++.so.6 => /projects/opt/gcc/4.8.3/lib64/libstdc++.so.6 (0x00002ad3b58e3000)
    libm.so.6 => /lib64/libm.so.6 (0x0000003166800000)
    libgcc_s.so.1 => /projects/opt/gcc/4.8.3/lib64/libgcc_s.so.1 (0x00002ad3b5bed000)
    libc.so.6 => /lib64/libc.so.6 (0x0000003166400000)
    /lib64/ld-linux-x86-64.so.2 (0x0000003166000000)