compiletest: normalize to $SRC_DIR_REAL before $TEST_BUILD_DIR

in case the real paths into the libstd/libcore are located inside the
the build directory, maybe because it's coming from an extracted dist
component in the build dir (cc opt-dist)

Author: Urgau

src/tools/compiletest/src/runtest.rs

@@ -2301,6 +2301,12 @@ impl<'test> TestCx<'test> {
 // eg. /home/user/rust/compiler
 normalize_path(&base_dir.join("compiler"),"$COMPILER_DIR");
 
+// Real paths into the libstd/libcore
+let rust_src_dir = &self.config.sysroot_base.join("lib/rustlib/src/rust");
+ rust_src_dir.try_exists().expect(&*format!("{} should exists", rust_src_dir.display()));
+let rust_src_dir = rust_src_dir.read_link().unwrap_or(rust_src_dir.to_path_buf());
+normalize_path(&rust_src_dir.join("library"),"$SRC_DIR_REAL");
+
 // Paths into the build directory
 let test_build_dir = &self.config.build_base;
 let parent_build_dir = test_build_dir.parent().unwrap().parent().unwrap().parent().unwrap();
@@ -2310,12 +2316,6 @@ impl<'test> TestCx<'test> {
 // eg. /home/user/rust/build
 normalize_path(parent_build_dir,"$BUILD_DIR");
 
-// Real paths into the libstd/libcore
-let rust_src_dir = &self.config.sysroot_base.join("lib/rustlib/src/rust");
- rust_src_dir.try_exists().expect(&*format!("{} should exists", rust_src_dir.display()));
-let rust_src_dir = rust_src_dir.read_link().unwrap_or(rust_src_dir.to_path_buf());
-normalize_path(&rust_src_dir.join("library"),"$SRC_DIR_REAL");
-
 if json {
 // escaped newlines in json strings should be readable
 // in the stderr files. There's no point int being correct,