build arm-clang on circleci with pull request (#2644)

* Build arm-clang using circle ci (only on PR): cache most of mandatory deps, clang toolchain
* update get_deps.py to include CMSIS_5 with --print + no arguments, prevent duplicated deps

tools/get_deps.py

@@ -249,9 +249,6 @@ def main():
     boards = args.board
     print_only = args.print
 
-    if len(families) == 0 and len(boards) == 0:
-        print("Warning: family and board are not specified, only fetching mandatory dependencies.")
-
     status = 0
     deps = list(deps_mandatory.keys())
 
@@ -267,11 +264,14 @@ def main():
 
         for f in families:
             for d in deps_optional:
-                if f in deps_optional[d][2]:
+                if d not in deps and f in deps_optional[d][2]:
                     deps.append(d)
 
     if print_only:
         pvalue = {}
+        # print only without arguments, always add CMSIS_5
+        if len(families) == 0 and len(boards) == 0:
+            deps.append('lib/CMSIS_5')
         for d in deps:
             commit = deps_all[d][1]
             pvalue[d] = commit