gcc: update to support compressed debug sections

Add a static build of zlib (1.2.8) required to support compressed debug
sections. Use static zlib for elfutils, binutils, and gcc.

Drop CXX and CXXCPP from elfutils, it's written only in C.

Add new options for GCC:
--enable-__cxa_atexit
--disable-libunwind-exceptions
--enable-gnu-unique-object
--enable-plugin
--with-linker-hash-style=gnu
--enable-linker-build-id
--disable-dssi

Fix $PATH; use 'eu-' program prefix for elfutils binaries.

Fix math support check in libstdc++v3 due to a typo in GCC configure CXXFLAGS.
Details:

    https://hypernews.cern.ch/HyperNews/CMS/get/sw-develtools/2033/1/1/1/1/1/1/1/1.html

Port of

    c3e7c45a574e631f359ee7582ab8fc357db19b0d
    7eca4a013bcd7dd7ab8654e3dae8eedd90fb07cf
    5db9aa94b2a5be33ae970534c379c57b3fa09f70

from IB/CMSSW_7_2_X/gcc491 to IB/CMSSW_7_2_X/stable
gcc-toolfile: add -Wno-psabi to CXXFLAGS

Should remove all

    AVX vector return without AVX enabled changes the ABI

warnings.

More details why we get them in CMSSW:

    https://hypernews.cern.ch/HyperNews/CMS/get/swReleases/4007.html

Port of

    490f80a928d5256809b3fd8a3d724d7ead43e51b

from IB/CMSSW_7_2_X/gcc491 to IB/CMSSW_7_2_X/stable
dwz: new external for DWARF optimization/compression

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
file-toolfile,cmssw-tool-conf: use file from CMSDIST

SLC6 contains too old file, which does not understand build IDs.
Use the one from CMSDIST, which can print build IDs.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
CMSSW and CORAL debug information

Build debug information for SCRAM projects CMSSW and CORAL.
Use zlib compressed debug sections and dwz based optimizations to
decrease the size.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
gcc-toolfile: Enable GAS to produce compressed debug sections

Enable GNU Assembler to produce compressed debug sections in objects
files for the linker. Improves linker performance.

Signed-off-by: David Abdurachmanov <David.Abdurachmanov@cern.ch>
fix the processing of debug symbols and the related subpackage functionality

  - generate debug information
  - relocate the source file information to a default directory (that GB can later remap)
  - split and compress the debugging symbols
  - package the debugging symbols in a separate sub-package