Bug#854692: pybind11: FTBFS due to an internal compiler error

[Ghislain Antony Vaillant <ghisvail@gmail.com>]

Package: gcc-6
Version: 6.3.0-6
Severity: important

Dear Maintainer,

I have tried to rebuild the pybind11 package [1] using an up-to-date
sbuild running unstable. The build succeeded in the past [2] but now
fails with an internal compiler error:

```
In file included from /<<PKGBUILDDIR>>/tests/pybind11_tests.h:2:0,
                 from /<<PKGBUILDDIR>>/tests/test_alias_initialization.cpp:11:
/<<PKGBUILDDIR>>/include/pybind11/pybind11.h:62:22: internal compiler error: in mangle_decl, at cp/mangle.c:3659
         initialize([f](Class *c, Arg... args) -> Return { return (c->*f)(args...); },
```

I will provide the corresponding build log.

Ghis


-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (900, 'testing'), (300, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 4.9.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages gcc-6 depends on:
ii  binutils      2.27.90.20170124-2
ii  cpp-6         6.3.0-5
ii  gcc-6-base    6.3.0-5
ii  libc6         2.24-9
ii  libcc1-0      6.3.0-5
ii  libgcc-6-dev  6.3.0-5
ii  libgcc1       1:6.3.0-5
ii  libgmp10      2:6.1.2+dfsg-1
ii  libisl15      0.18-1
ii  libmpc3       1.0.3-1
ii  libmpfr4      3.1.5-1
ii  libstdc++6    6.3.0-5
ii  zlib1g        1:1.2.8.dfsg-5

Versions of packages gcc-6 recommends:
ii  libc6-dev  2.24-9

Versions of packages gcc-6 suggests:
pn  gcc-6-doc         <none>
pn  gcc-6-locales     <none>
pn  gcc-6-multilib    <none>
pn  libasan3-dbg      <none>
pn  libatomic1-dbg    <none>
pn  libcilkrts5-dbg   <none>
pn  libgcc1-dbg       <none>
pn  libgomp1-dbg      <none>
pn  libitm1-dbg       <none>
pn  liblsan0-dbg      <none>
pn  libmpx2-dbg       <none>
pn  libquadmath0-dbg  <none>
pn  libtsan0-dbg      <none>
pn  libubsan0-dbg     <none>

-- no debconf information