c_build_helper.py: Move compile to helper

Move compilation to a separate helper function in c_build_helper.py to
allow more generic use.

Signed-off-by: David Horstmann <david.horstmann@arm.com>

scripts/mbedtls_dev/c_build_helper.py

@@ -89,6 +89,27 @@ int main(void)
 }
 ''')
 
+def compile_c_file(c_filename, exe_filename, include_dirs):
+    cc = os.getenv('CC', 'cc')
+    cmd = [cc]
+
+    proc = subprocess.Popen(cmd,
+                            stdout=subprocess.DEVNULL,
+                            stderr=subprocess.PIPE,
+                            universal_newlines=True)
+    cc_is_msvc = 'Microsoft (R) C/C++' in proc.communicate()[1]
+
+    cmd += ['-I' + dir for dir in include_dirs]
+    if cc_is_msvc:
+        # MSVC has deprecated using -o to specify the output file,
+        # and produces an object file in the working directory by default.
+        obj_filename = exe_filename[:-4] + '.obj'
+        cmd += ['-Fe' + exe_filename, '-Fo' + obj_filename]
+    else:
+        cmd += ['-o' + exe_filename]
+
+    subprocess.check_call(cmd + [c_filename])
+
 def get_c_expression_values(
         cast_to, printf_format,
         expressions,
@@ -128,24 +149,8 @@ def get_c_expression_values(
                                                          expressions)
         )
         c_file.close()
-        cc = os.getenv('CC', 'cc')
-        cmd = [cc]
 
-        proc = subprocess.Popen(cmd,
+        compile_c_file(c_name, exe_name, include_path)
-                                stdout=subprocess.DEVNULL,
-                                stderr=subprocess.PIPE,
-                                universal_newlines=True)
-        cc_is_msvc = 'Microsoft (R) C/C++' in proc.communicate()[1]
-
-        cmd += ['-I' + dir for dir in include_path]
-        if cc_is_msvc:
-            # MSVC has deprecated using -o to specify the output file,
-            # and produces an object file in the working directory by default.
-            obj_name = exe_name[:-4] + '.obj'
-            cmd += ['-Fe' + exe_name, '-Fo' + obj_name]
-        else:
-            cmd += ['-o' + exe_name]
-        subprocess.check_call(cmd + [c_name])
         if keep_c:
             sys.stderr.write('List of {} tests kept at {}\n'
                              .format(caller, c_name))