tests/vm: Clean out old working directories on build

When we do a build inside one of the BSD VMs, first
delete any stale old build directories from the VM's
/var/tmp. This prevents the VM from running out of
disk space after it has been used for a dozen or
so builds.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Fam Zheng <famz@redhat.com>
Message-id: 20180820124811.7982-1-peter.maydell@linaro.org
diff --git a/tests/vm/freebsd b/tests/vm/freebsd
index 0a6ec46..b698312 100755
--- a/tests/vm/freebsd
+++ b/tests/vm/freebsd
@@ -20,6 +20,7 @@
     name = "freebsd"
     BUILD_SCRIPT = """
         set -e;
+        rm -rf /var/tmp/qemu-test.*
         cd $(mktemp -d /var/tmp/qemu-test.XXXXXX);
         tar -xf /dev/vtbd1;
         ./configure {configure_opts};
diff --git a/tests/vm/netbsd b/tests/vm/netbsd
index 45c9260..a4e2582 100755
--- a/tests/vm/netbsd
+++ b/tests/vm/netbsd
@@ -20,6 +20,7 @@
     name = "netbsd"
     BUILD_SCRIPT = """
         set -e;
+        rm -rf /var/tmp/qemu-test.*
         cd $(mktemp -d /var/tmp/qemu-test.XXXXXX);
         tar -xf /dev/rld1a;
         ./configure --python=python2.7 {configure_opts};
diff --git a/tests/vm/openbsd b/tests/vm/openbsd
index 98edfbc..52500ee 100755
--- a/tests/vm/openbsd
+++ b/tests/vm/openbsd
@@ -20,6 +20,7 @@
     name = "openbsd"
     BUILD_SCRIPT = """
         set -e;
+        rm -rf /var/tmp/qemu-test.*
         cd $(mktemp -d /var/tmp/qemu-test.XXXXXX);
         tar -xf /dev/rsd1c;
         ./configure --cc=x86_64-unknown-openbsd6.1-gcc-4.9.4 --python=python2.7 {configure_opts};