Revert "dependencies: ensure that DESTDIR isn't set when running Buildroot"

We should instead simply unset it at runtime, like we do for
PKG_CONFIG_PATH.

This reverts commit 9910eba33a.

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>

support/dependencies/dependencies.sh

@@ -48,12 +48,6 @@ if test -n "$PERL_MM_OPT" ; then
     exit 1
 fi
 
-if test -n "$DESTDIR" ; then
-    /bin/echo -e "\nYou have the DESTDIR environment variable set. Please"
-    /bin/echo -e "unset it so that Buildroot can work properly."
-    exit 1
-fi
-
 # Verify that which is installed
 if ! which which > /dev/null ; then
 	/bin/echo -e "\nYou must install 'which' on your build machine\n";