Require GCC 7 and enable C++17

Fix MSVC2019
- result type of conditional expression is ambiguous:
  types 'const char [1]' and 'QByteArray' can be converted
  to multiple common types

Fix MinGW 8.1
- undefined reference to SemanticHighlightNotification::methodName

Fix Utils::transform with std::vector for GCC & MSVC

Unfortunately we cannot get rid of the special variant and optional
implementations, because Apple Clang requires deployment target >= 10.14
for the functions that can throw std::bad_optional_access.

Fixes: QTCREATORBUG-20520
Change-Id: I5c36a70f21f8b0215d2f4fc5c0653a022778d928
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
Reviewed-by: Marco Bubke <marco.bubke@qt.io>
Reviewed-by: David Schulz <david.schulz@qt.io>

1 files changed, 2 insertions, 2 deletions

diff --git a/README.md b/README.md
index 6daded0a4f..41438e0153 100644
--- a/README.md
+++ b/README.md
@@ -31,11 +31,11 @@ Prerequisites:
 * Qt WebEngine module for QtWebEngine based help viewer
 * On Windows:
     * ActiveState Active Perl
-    * MinGW with g++ 5.3 or Visual Studio 2017 or later
+    * MinGW with GCC 7 or Visual Studio 2017 or later
     * jom
     * Python 3.5 or later (optional, needed for the python enabled debug helper)
 * On Mac OS X: latest Xcode
-* On Linux: g++ 5.3 or later
+* On Linux: GCC 7 or later
 * LLVM/Clang 8.0.0 or later (optional, needed for the Clang Code Model, Clang Tools, ClangFormat,
   Clang PCH Manager and Clang Refactoring plugins, see the section
   "Get LLVM/Clang for the Clang Code Model". The LLVM C++ API provides no compatibility garantee,