Fix validation regexes to handle rc version numbers.

test cases/failing/130 invalid ast/test.json

@@ -2,7 +2,7 @@
   "stdout": [
     {
       "match": "re",
-      "line": "test cases/failing/130 invalid ast/meson.build:1:44: ERROR: Meson version is [0-9.]+ but project requires 0.1.0"
+      "line": "test cases/failing/130 invalid ast/meson.build:1:44: ERROR: Meson version is [0-9.]+(\\.rc[0-9]+)? but project requires 0.1.0"
     }
   ]
 }

test cases/failing/131 invalid project function/test.json

@@ -2,7 +2,7 @@
   "stdout": [
     {
       "match": "re",
-      "line": "test cases/failing/131 invalid project function/meson.build:1:67: ERROR: Meson version is [0-9.]+ but project requires 0.1.0"
+      "line": "test cases/failing/131 invalid project function/meson.build:1:67: ERROR: Meson version is [0-9.]+(\\.rc[0-9]+)? but project requires 0.1.0"
     }
   ]
 }