build: Pass NO_LIBELF etc. to ppc64 perf builds on ppc64le

When building ppc64 perf on ppc64le the container image doesn't have
many libraries, eg. libelf (because the distro doesn't cross build them
for ppc64).

So to make the build work pass NO_LIBELF etc.

Author: mpe

build/scripts/container-build.sh

@@ -164,7 +164,7 @@ elif [[ "$1" == "docs" ]]; then
 elif [[ "$1" == "perf" ]]; then
     cmd="make $quiet -C tools/perf O=/output"
 
-    if [[ $(uname -m) != "ppc64le" ]]; then
+    if [[ $(uname -m) != "ppc64le" || $CROSS_COMPILE == "powerpc64-linux-gnu-" ]]; then
         cmd+=" NO_LIBELF=1 NO_LIBTRACEEVENT=1"
     fi