$ spack install -j16 --restage flang%[email protected]
...
==> Already staged flang-develop-j6mkvco2dtnaaev2fxpxqnnx33fg4rx5 in /home/certik/repos/spack/var/spack/stage/flang-develop-j6mkvco2dtnaaev2fxpxqnnx33fg4rx5
==> No patches needed for flang
==> Building flang [CMakePackage]
==> Executing phase: 'cmake'
==> Error: ProcessError: Command exited with status 1:
    'cmake' '/home/certik/repos/spack/var/spack/stage/flang-develop-j6mkvco2dtna
aev2fxpxqnnx33fg4rx5/flang' '-G' 'Unix Makefiles' '-DCMAKE_INSTALL_PREFIX:PATH=/
home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/flang-devel
op-j6mkvco2dtnaaev2fxpxqnnx33fg4rx5' '-DCMAKE_BUILD_TYPE:STRING=RelWithDebInfo' 
'-DCMAKE_VERBOSE_MAKEFILE:BOOL=ON' '-DCMAKE_INSTALL_RPATH_USE_LINK_PATH:BOOL=FAL
SE' '-DCMAKE_INSTALL_RPATH:STRING=/home/certik/repos/spack/opt/spack/linux-ubunt
u16.04-x86_64/gcc-6.4.0/flang-develop-j6mkvco2dtnaaev2fxpxqnnx33fg4rx5/lib:/home
/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/flang-develop-j
6mkvco2dtnaaev2fxpxqnnx33fg4rx5/lib64:/home/certik/repos/spack/opt/spack/linux-u
buntu16.04-x86_64/gcc-6.4.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/lib:/hom
e/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/binutils-2.28-
atc354dhdpdup3pgboge4w4rizlvpguf/lib:/home/certik/repos/spack/opt/spack/linux-ub
untu16.04-x86_64/gcc-6.4.0/gettext-0.19.8.1-z4rue2xloo4gjfujlq72wc53xqcrwqfa/lib
:/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/bzip2-1.0
.6-bmyxoqbr52auiqqupsmixp65chxmnwuu/lib:/home/certik/repos/spack/opt/spack/linux
-ubuntu16.04-x86_64/gcc-6.4.0/libxml2-2.9.4-zqliw5yhxo4ijx4vhjeb6hdgjv2hu6ep/lib
:/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/xz-5.2.3-
2tho6an2mngb5ym2qvv6jfjppr2aw2bj/lib:/home/certik/repos/spack/opt/spack/linux-ub
untu16.04-x86_64/gcc-6.4.0/zlib-1.2.11-yvlwvyz4fbdmewglmq46o6ivkrczvigf/lib:/hom
e/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/ncurses-6.0-jt
mz6tz4l5uwnx4ngi2sbqkdbqrpvmbm/lib:/home/certik/repos/spack/opt/spack/linux-ubun
tu16.04-x86_64/gcc-6.4.0/libedit-3.1-20170329-hrqaevtd5acrbcmflznjpffig6txuo56/l
ib:/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/python-
2.7.14-n6pbabvjb3a3wfoo75k5s7ossot2kzyi/lib:/home/certik/repos/spack/opt/spack/l
inux-ubuntu16.04-x86_64/gcc-6.4.0/openssl-1.0.2k-ztgs5rpiobj7tpyccjzesbvdyk6p3f3
i/lib:/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/read
line-7.0-323dutestkw2xm64b2flv7p334ux2hbx/lib:/home/certik/repos/spack/opt/spack
/linux-ubuntu16.04-x86_64/gcc-6.4.0/sqlite-3.20.0-25axhq64ozc5mhqogrgmad2gzh4g4q
4k/lib:/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/pcr
e-8.40-nx2htpr5kmlrvcfzln4n33qx6ff3lg4h/lib' '-DCMAKE_PREFIX_PATH:STRING=/home/c
ertik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/llvm-5.0.0-vvs4bk
sw5ihlpljb57bhhkczdgpccsaa;/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-
x86_64/gcc-6.4.0/cmake-3.9.4-t2ydlbo7cmuwscboipwjj34sulgog5gq' '-DWITH_WERROR=OF
F' '-DCMAKE_C_COMPILER=/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_
64/gcc-6.4.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/bin/clang' '-DCMAKE_CXX
_COMPILER=/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/
llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/bin/clang++' '-DCMAKE_Fortran_COMPIL
ER=/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/llvm-5.
0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/bin/flang' '-DFLANG_LIBOMP=/home/certik/rep
os/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4.0/llvm-5.0.0-vvs4bksw5ihlplj
b57bhhkczdgpccsaa/lib/libomp.so'

6 errors found in build log:
     [ ... ]
     7     -- Detecting C compiler ABI info
     8     -- Detecting C compiler ABI info - done
     9     -- Detecting C compile features
     10    -- Detecting C compile features - done
     11    -- Check for working CXX compiler: /home/certik/repos/spack/opt/spack
/linux-ubuntu16.04-x86_64/gcc-6.4.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/
bin/clang++
     12    -- Check for working CXX compiler: /home/certik/repos/spack/opt/spack
/linux-ubuntu16.04-x86_64/gcc-6.4.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/
bin/clang++ -- broken
  >> 13    CMake Error at /home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x
86_64/gcc-6.4.0/cmake-3.9.4-t2ydlbo7cmuwscboipwjj34sulgog5gq/share/cmake-3.9/Mod
ules/CMakeTestCXXCompiler.cmake:44 (message):
     14      The C++ compiler
     15      "/home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.
4.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/bin/clang++"
     16      is not able to compile a simple test program.
     17    
     18      It fails with the following output:
     19    
     [ ... ]
     45      -E cmake_link_script CMakeFiles/cmTC_005a3.dir/link.txt --verbose=1
     46    
     47    
     48      /home/certik/repos/spack/opt/spack/linux-ubuntu16.04-x86_64/gcc-6.4
.0/llvm-5.0.0-vvs4bksw5ihlpljb57bhhkczdgpccsaa/bin/clang++
     49      -rdynamic CMakeFiles/cmTC_005a3.dir/testCXXCompiler.cxx.o -o cmTC_0
05a3
     50    
  >> 51    ld: cannot find -lstdc++
     52    
  >> 53      clang-5.0: error: linker command failed with exit code 1 (use -v to
 see
     54      invocation)
     55    
  >> 56      CMakeFiles/cmTC_005a3.dir/build.make:97: recipe for target 'cmTC_00
5a3'
     57      failed
     58    
  >> 59      make[1]: *** [cmTC_005a3] Error 1
     60    
     61      make[1]: Leaving directory
     62      '/home/certik/tmp/spack-stage/spack-stage-T8eI00/flang/spack-build/
CMakeFiles/CMakeTmp'
     63    
     64    
     65      Makefile:126: recipe for target 'cmTC_005a3/fast' failed
     66    
  >> 67    make: *** [cmTC_005a3/fast] Error 2
     68    
     69    
     70    
     71    
     72    
     73      CMake will not be able to correctly generate this project.

See build log for details:
  /home/certik/repos/spack/var/spack/stage/flang-develop-j6mkvco2dtnaaev2fxpxqnn
x33fg4rx5/flang/spack-build.out