Relax conditions in rustdoc test cfg flags tests.

In Windows the rustdoc test output sets more double quotes, so
the test doesn't pass. We need to relax the test so it pass in
*NIX and Windows environments.

tests/test.rs

@@ -2273,11 +2273,11 @@ fn pass_correct_cfgs_flags_to_rustdoc() {
             authors = []
 
             [features]
-            default = ["a/default"]
-            nightly = ["a/nightly"]
+            default = ["feature_a/default"]
+            nightly = ["feature_a/nightly"]
 
-            [dependencies.a]
-            path = "libs/a"
+            [dependencies.feature_a]
+            path = "libs/feature_a"
             default-features = false
         "#)
         .file("src/lib.rs", r#"
@@ -2289,9 +2289,9 @@ fn pass_correct_cfgs_flags_to_rustdoc() {
                 }
             }
         "#)
-        .file("libs/a/Cargo.toml", r#"
+        .file("libs/feature_a/Cargo.toml", r#"
             [package]
-            name = "a"
+            name = "feature_a"
             version = "0.1.0"
             authors = []
 
@@ -2305,7 +2305,7 @@ fn pass_correct_cfgs_flags_to_rustdoc() {
             [build-dependencies]
             serde_codegen = { version = "0.8", optional = true }
         "#)
-        .file("libs/a/src/lib.rs", r#"
+        .file("libs/feature_a/src/lib.rs", r#"
             #[cfg(feature = "serde_derive")]
             const MSG: &'static str = "This is safe";
 
@@ -2318,17 +2318,17 @@ fn pass_correct_cfgs_flags_to_rustdoc() {
         "#);
 
     assert_that(p.cargo_process("test")
-                .arg("--package").arg("a")
+                .arg("--package").arg("feature_a")
                 .arg("--verbose"),
                 execs().with_status(0)
                        .with_stderr_contains("\
-[DOCTEST] a
-[RUNNING] `rustdoc --test [..]--cfg feature=\\\"serde_codegen\\\"[..]`"));
+[DOCTEST] feature_a
+[RUNNING] `rustdoc --test [..]serde_codegen[..]`"));
 
     assert_that(p.cargo_process("test")
                 .arg("--verbose"),
                 execs().with_status(0)
                        .with_stderr_contains("\
 [DOCTEST] foo
-[RUNNING] `rustdoc --test [..]--cfg feature=\\\"a\\\"[..]`"));
+[RUNNING] `rustdoc --test [..]feature_a[..]`"));
 }