scons detects standalone MSVC on Windows

Under Windows, Scons is now capable of detecting and compiling with
standalone MSVC compilers (aka "Visual C++ Build Tools").
http://landinghub.visualstudio.com/visual-cpp-build-tools

Tried with version 2015, and native x86 and x64 compilers under
Windows 10 pro 64 and Windows 8.1 64, with the default Win8 SDK
provided by the "Visual C++ Build Tools" web-installer.

Follow the same compiling instructions than for compiling with Visual
Studio, except that Visual Studio is no more required.

KNOWN ISSUES :
- ``methods.detect_visual_c_compiler_version()`` will emit a warning message
on computers where the ``VSINSTALLDIR`` environement variable is not present.
But it should compile just fine and still automatically detects the 32 or
64 bits according to the compiler you picked.

TODO :
- eventually, update ``platform/winrt/dectet.py`` with function
``methods.msvc_is_detected()`` and try to compile winrt/UWP with
these standalone compilers (if you did not select Win10 SDK when
installing the standalone tools, you can run it again).
- update doc to make users aware of "Visual C++ Build Tools" aka
"stadalone MSVC".
- eventually, update ``methods.detect_visual_c_compiler_version()``

1 files changed, 2 insertions, 1 deletions

diff --git a/drivers/builtin_openssl2/SCsub b/drivers/builtin_openssl2/SCsub
index a28bc2922c..0c035cc4a5 100644
--- a/drivers/builtin_openssl2/SCsub
+++ b/drivers/builtin_openssl2/SCsub
@@ -656,7 +656,8 @@ if "platform" in env and env["platform"] == "winrt":
 
 # Workaround for compilation error with GCC/Clang when -Werror is too greedy (GH-4517)
 import os
-if not (os.name=="nt" and os.getenv("VSINSTALLDIR")!=None): # not Windows and not MSVC
+import methods
+if not (os.name=="nt" and methods.msvc_is_detected() ): # not Windows and not MSVC
 	env_drivers.Append(CFLAGS=["-Wno-error=implicit-function-declaration"])
 
 env_drivers.add_source_files(env.drivers_sources,openssl_sources)