sdk_lib/sdk_entry.sh: use a login shell to source /etc/profile

For execution of the compiled binaries in /build/arm64-usr we rely on
qemu-user binfmt emulation and have to tell it where the root is with
QEMU_LD_PREFIX because build systems don't chroot into /build/arm64-usr
themselves (which also works just by chance on amd64 because we have
similar glibc versions and so on). The env var setup was done in
/etc/profile.d/qemu-aarch64.sh but is now not read anymore since the
container runs the shell not as login shell.

Add the login options to the bash and su calls when starting the
container.

sdk_lib/sdk_entry.sh

@@ -22,7 +22,7 @@ chown -R sdk:sdk /home/sdk
 #    our quotes for su -c "<cmd>" already.
 if [ $# -gt 0 ] ; then
     cmd="/home/sdk/.cmd"
-    echo -n "exec bash -i -c '" >"$cmd"
+    echo -n "exec bash -l -i -c '" >"$cmd"
     for arg in "$@"; do
         echo -n "\"$arg\" " >>"$cmd"
     done
@@ -33,5 +33,5 @@ if [ $# -gt 0 ] ; then
     rm -f "$cmd"
     exit $rc
 else
-    exec sudo su sdk
+    exec sudo su -l sdk
 fi