scripts: build-all: Build dtbs as part of 'all' builds

Make sure to build the dtb targets so that these are tested as part of
building all targets.

Change-Id: I351527d197ef6a60fefe43f3a16b34be86a74dd1
Signed-off-by: David Brown <davidb@codeaurora.org>

scripts/build-all.py

@@ -41,7 +41,7 @@ import sys
 version = 'build-all.py, version 0.01'
 
 build_dir = '../all-kernels'
-make_command = ["vmlinux", "modules"]
+make_command = ["vmlinux", "modules", "dtbs"]
 make_env = os.environ
 make_env.update({
         'ARCH': 'arm',