run: allow to pass environment variable to the VM

This change uses the .bash_profile file from the home directory that
is mounted in the VM to pass/update environment variables:
 - append the kernel tools path to PATH, this allows to access bpftool
   in the VM;
 - export the kernel build directory to get access to bpf build object.

The objective is to be able to start an MPTCP bpf scheduler and
validates its behavior using packetdrill.

Signed-off-by: Gregory Detal <gregory.detal@gmail.com>

entrypoint.sh

@@ -78,10 +78,14 @@ VIRTME_EXPECT_BOOT_TIMEOUT="300"
 
 KERNEL_SRC="${PWD}"
 
+# used to pass environment variables to the VM
+BASH_PROFILE="/root/.bash_profile"
+
 VIRTME_WORKDIR="${KERNEL_SRC}/.virtme"
 VIRTME_BUILD_DIR="${VIRTME_WORKDIR}/build"
 VIRTME_SCRIPTS_DIR="${VIRTME_WORKDIR}/scripts"
 VIRTME_PERF_DIR="${VIRTME_BUILD_DIR}/tools/perf"
+VIRTME_TOOLS_SBIN_DIR="${VIRTME_BUILD_DIR}/tools/sbin"
 
 VIRTME_KCONFIG="${VIRTME_BUILD_DIR}/.config"
 
@@ -613,6 +617,12 @@ prepare() { local mode no_tap=1
 		no_tap=0 # we want subtests
 	fi
 
+	cat <<EOF > "${BASH_PROFILE}"
+export KERNEL_BUILD_DIR="${VIRTME_BUILD_DIR}"
+export KERNEL_SRC_DIR="${KERNEL_SRC}"
+export PATH="\${PATH}:${VIRTME_TOOLS_SBIN_DIR}"
+EOF
+
 	cat <<EOF > "${VIRTME_SCRIPT}"
 #! /bin/bash