[machdep] use markdown backtick to delimit typenames in tests

Workaround odd gcc behavior in which `'` gets escaped as `\'` in diagnostic

share/machdeps/make_machdep/make_machdep.py

@@ -191,7 +191,7 @@ def find_value(name, typ, output):
             return int(x)
 
     elif typ == "type":
-        expected = "'([^']+)'"
+        expected = "`([^`]+)`"
 
         def conversion(x):
             return x

share/machdeps/make_machdep/make_machdep_common.h

@@ -39,6 +39,6 @@
 #define mkstr(s) #s
 
 #define TEST_TYPE_COMPATIBLE(T1, T2)                                           \
-  _Static_assert(!COMPATIBLE(T1, T2), "" mkstr(T2) " is '" #T1 "'");
+  _Static_assert(!COMPATIBLE(T1, T2), "" mkstr(T2) " is `" #T1 "`");
 
 #define TEST_TYPE_IS(type) TEST_TYPE_COMPATIBLE(type, TEST_TYPE)