* Use separate build directory for gzip
At least on mac systems (perhaps because of a case sensitivity issue?)
gzip fails to build inside the source tree:
```
config.status: linking /var/folders/fy/x2xtwh1n7fn0_0q2kk29xkv9vvmbqb/T/spack-stage/s3j/spack-stage-gzip-1.10-iatwtuk2l5xgwmuh4pwu5bf27yezpydj/spack-src/GNUmakefile to GNUmakefile
config.status: executing depfiles commands
==> Executing phase: 'build'
==> [2020-02-14-09:32:45.502913] 'make' '-j12'
make: GNUmakefile: Too many levels of symbolic links
make: stat: GNUmakefile: Too many levels of symbolic links
make: *** No rule to make target `GNUmakefile'. Stop.
```
* Simplify build directory and add gmake dependency
Libmng only needs gzip to compress man files for distribution, so it
builds fine without it. The spack
gzip currently fails to compile.
```
config.status: linking /var/folders/fy/x2xtwh1n7fn0_0q2kk29xkv9vvmbqb/T/spack-stage/s3j/spack-stage-gzip-1.10-iatwtuk2l5xgwmuh4pwu5bf27yezpydj/spack-src/GNUmakefile to GNUmakefile
config.status: executing depfiles commands
==> Executing phase: 'build'
==> [2020-02-14-09:32:45.502913] 'make' '-j12'
make: GNUmakefile: Too many levels of symbolic links
make: stat: GNUmakefile: Too many levels of symbolic links
make: *** No rule to make target `GNUmakefile'. Stop.
```
* Modify Flang NVidia GPU variant to make use of built-in CudaPackage
* Add OpenMP Offload patch if March 2019 compiler is selected.
* Flang parallel build has a race condition.
* llvm-flang now uses built-in CudaPackage.
* Add variant for different build releases.
* Fix OpenMP target offload for NVidia GPUs.
* Additional commong flags that are needed with comments.
* NVidia BC required for libomp target requires special treatment. Use clang built in previous step to re-compile libomptarget.
* Add a new package: Metall
* Fix errors in metall/package.py
* Update var/spack/repos/builtin/packages/metall/package.py
Change to https style URL
Co-Authored-By: Adam J. Stewart <ajstewart426@gmail.com>
* Update in metall/package.py. Change Metall to depend on Boost always
* Update in metall/package.py. Change to install Boost with the default variants
* Update metall/package.py. Removed a comment
Co-authored-by: Adam J. Stewart <ajstewart426@gmail.com>