Merge pull request #7722 from theotherjimmy/fix-arm-small-lib

Fix Microlib compatibility for -t ARM

Author: Cruz Monrreal

tools/toolchains/arm.py

@@ -63,8 +63,12 @@ def __init__(self, target, notify=None, macros=None,
         if getattr(target, "default_lib", "std") == "small":
             if "-DMBED_RTOS_SINGLE_THREAD" not in self.flags['common']:
                 self.flags['common'].append("-DMBED_RTOS_SINGLE_THREAD")
+            if "-D__MICROLIB" not in self.flags['common']:
+                self.flags['common'].append("-D__MICROLIB")
             if "--library_type=microlib" not in self.flags['ld']:
                 self.flags['ld'].append("--library_type=microlib")
+            if "--library_type=microlib" not in self.flags['common']:
+                self.flags['common'].append("--library_type=microlib")
 
         if target.core == "Cortex-M0+":
             cpu = "Cortex-M0"