Bug#919577: g++-8: Can't build GN tool due to bug in raw-string parsing

[Allan Sandfeld Jensen <debian@carewolf.com>]

Package: g++-8
Version: 8.2.0-14
Severity: serious

Can not compile code with something looking like a precompiler directive inside
a raw-string. For instance code like this:

const char kFormat_Help[] =
    R"(gn format [--dump-tree] (--stdin | <build_file>)

  Formats .gn file to a standard format.

  The contents of some lists ('sources', 'deps', etc.) will be sorted to a
  canonical order. To suppress this, you can add a comment of the form "#
  NOSORT" immediately preceding the assignment. e.g.

  # NOSORT
  sources = [
    "z.cc",
    "a.cc",
  ]
)";

The compiler complains it doesn't understand the #NOSORT directive.

I can not reproduce the issue with upstream g++-8 or with g++-7, it appears to be a serious
flaw in specifically this Debian version of g++-8.

-- System Information:
Debian Release: buster/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (500, 'testing'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.19.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8), LANGUAGE=en_GB:en_US (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages g++-8 depends on:
ii  gcc-8            8.2.0-14
ii  gcc-8-base       8.2.0-14
ii  libc6            2.28-5
ii  libgmp10         2:6.1.2+dfsg-4
ii  libisl19         0.20-2
ii  libmpc3          1.1.0-1
ii  libmpfr6         4.0.2~rc1-1
ii  libstdc++-8-dev  8.2.0-14
ii  zlib1g           1:1.2.11.dfsg-1

g++-8 recommends no packages.

Versions of packages g++-8 suggests:
ii  g++-8-multilib    8.2.0-14
pn  gcc-8-doc         <none>
pn  libstdc++6-8-dbg  <none>

-- no debconf information