pkg/52395: pkgtools/pbulk-base fails to comile with GCC 6

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>Number:         52395
>Category:       pkg
>Synopsis:       pkgtools/pbulk-base fails to comile with GCC 6
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jul 11 22:25:00 +0000 2017
>Originator:     Sevan Janiyan
>Release:        pkgsrc-current
>Organization:
>Environment:
Linux pkgsrc 4.9.0-3-amd64 #1 SMP Debian 4.9.30-2 (2017-06-12) x86_64 GNU/Linux

>Description:
Attamepting to setup a bulk build env on Debian 9 with prefer-pkgsrc set to yes, pbulk build process fail with the following

cc -O2 -D_FORTIFY_SOURCE=2  -Wall -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wno-uninitialized -Wreturn-type -Wcast-qual -Wpointer-arith -Wwrite-strings -Wswitch -Wshadow -Werror
 -DHAVE_NBCOMPAT_H=1 -I/tmp/obj-pbulk/pkgtools/pbulk-base/work/libnbcompat -D_GNU_SOURCE -c exec.c
exec.c: In function 'fork_chdir_exec':
exec.c:71:3: error: ignoring return value of 'write', declared with attribute warn_unused_result [-Werror=unused-result]
   (void)write(STDERR_FILENO, chdir_err, sizeof(chdir_err) - 1);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
exec.c:72:3: error: ignoring return value of 'write', declared with attribute warn_unused_result [-Werror=unused-result]
   (void)write(STDERR_FILENO, dir, strlen(dir));
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
exec.c:73:3: error: ignoring return value of 'write', declared with attribute warn_unused_result [-Werror=unused-result]
   (void)write(STDERR_FILENO, "\".\n", 3);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
exec.c:78:4: error: ignoring return value of 'write', declared with attribute warn_unused_result [-Werror=unused-result]
    (void)write(STDERR_FILENO, dup2_err, sizeof(dup2_err) - 1);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors



$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --with-target-s
 ystem-zlib --enable-objc-gc=auto --enable-multiarch --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
gcc version 6.3.0 20170516 (Debian 6.3.0-18)


>How-To-Repeat:

>Fix: