fix arm compiler static ram memory statistics

don't count ARM_LIB_HEAP in static RAM pool

Original Mbed OS PR[#1256](#1246)

(cherry picked from commit c69e77c)
Signed-off-by: Janne Kiiskila <[email protected]>

Author: maciejbocianski

tools/memap.py

@@ -280,7 +280,10 @@ def parse_section(self, line):
         """  # noqa: E501
         test_re = re.match(self.RE, line)
 
-        if test_re:
+        if (
+            test_re
+            and "ARM_LIB_HEAP" not in line
+            ):
             size = int(test_re.group(2), 16)
 
             if test_re.group(4) == 'RO':