use a configurable location for apport report storage

Hardcoding /var/crash means we can't test it properly and it isn't
really our style.

apt-pkg/deb/dpkgpm.cc

@@ -1741,7 +1741,8 @@ void pkgDPkgPM::WriteApportReport(const char *pkgpath, const char *errormsg)
    //    we overwrite it. This is the same behaviour as apport
    // - if we have a report with the same pkgversion already
    //   then we skip it
-   reportfile = flCombine("/var/crash",pkgname+".0.crash");
+   _config->CndSet("Dir::Apport", "var/crash");
+   reportfile = flCombine(_config->FindDir("Dir::Apport", "var/crash"), pkgname+".0.crash");
    if(FileExists(reportfile))
    {
       struct stat buf;

test/integration/framework

@@ -298,7 +298,7 @@ setupenvironment() {
 	mkdir rootdir aptarchive keys
 	cd rootdir
 	mkdir -p etc/apt/apt.conf.d etc/apt/sources.list.d etc/apt/trusted.gpg.d etc/apt/preferences.d
-	mkdir -p usr/bin var/cache var/lib var/log tmp
+	mkdir -p usr/bin var/cache var/lib var/log var/crash tmp
 	mkdir -p var/lib/dpkg/info var/lib/dpkg/updates var/lib/dpkg/triggers
 	mkdir -p usr/lib/apt/solvers usr/lib/apt/planners
 	touch var/lib/dpkg/available

test/integration/test-apt-progress-fd-error

@@ -12,6 +12,7 @@ touch usr/bin/file-conflict
 
 buildsimplenativepackage 'foo1' 'native' '0.8.15' 'stable' '' 'pkg with file conflicts' '' '' 'usr/'
 buildsimplenativepackage 'foo2' 'native' '0.8.15' 'stable' '' 'pkg with file conflicts' '' '' 'usr/'
+insertinstalledpackage 'apport' 'native' '1'
 
 setupaptarchive
 
@@ -19,3 +20,6 @@ exec 3> apt-progress.log
 testfailure aptget install foo1 foo2 -y -o APT::Status-Fd=3
 msgtest 'Ensure correct error message'
 testsuccess --nomsg grep "aptarchive/pool/foo2_0.8.15_[^.]\+.deb:36.3636:trying to overwrite '/usr/bin/file-conflict', which is also in package foo1 0.8.15" apt-progress.log
+
+testsuccess test -s rootdir/var/crash/foo2.0.crash
+testsuccess grep '^Package: foo2 0.8.15$' rootdir/var/crash/foo2.0.crash