Remove support for building with Visual Studio 2017. Since Jan 29, 2022, upstream LLVM has required VS2019 or VS2022 to build. So it has not been possible to build emsdk from source with VS2017 for a year. 058c5dfc78 (#1178)

emsdk.py

@@ -257,13 +257,6 @@ def vswhere(version):
       program_files = os.environ['ProgramFiles']
     vswhere_path = os.path.join(program_files, 'Microsoft Visual Studio', 'Installer', 'vswhere.exe')
     output = json.loads(subprocess.check_output([vswhere_path, '-latest', '-version', '[%s.0,%s.0)' % (version, version + 1), '-requires', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64', '-property', 'installationPath', '-format', 'json']))
-    # Visual Studio 2017 Express is not included in the above search, and it
-    # does not have the VC.Tools.x86.x64 tool, so do a catch-all attempt as a
-    # fallback, to detect Express version.
-    if not output:
-      output = json.loads(subprocess.check_output([vswhere_path, '-latest', '-version', '[%s.0,%s.0)' % (version, version + 1), '-products', '*', '-property', 'installationPath', '-format', 'json']))
-      if not output:
-        return ''
     return str(output[0]['installationPath'])
   except Exception:
     return ''
@@ -288,16 +281,10 @@ if WINDOWS:
     CMAKE_GENERATOR = 'Visual Studio 17'
   elif '--vs2019' in sys.argv:
     CMAKE_GENERATOR = 'Visual Studio 16'
-  elif '--vs2017' in sys.argv:
-    CMAKE_GENERATOR = 'Visual Studio 15'
   elif len(vswhere(17)) > 0:
     CMAKE_GENERATOR = 'Visual Studio 17'
   elif len(vswhere(16)) > 0:
     CMAKE_GENERATOR = 'Visual Studio 16'
-  elif len(vswhere(15)) > 0:
-    # VS2017 has an LLVM build issue, see
-    # https://github.com/kripken/emscripten-fastcomp/issues/185
-    CMAKE_GENERATOR = 'Visual Studio 15'
   elif which('mingw32-make') is not None and which('g++') is not None:
     CMAKE_GENERATOR = 'MinGW Makefiles'
   else:
@@ -305,7 +292,7 @@ if WINDOWS:
     CMAKE_GENERATOR = ''
 
 
-sys.argv = [a for a in sys.argv if a not in ('--mingw', '--vs2017', '--vs2019', '--vs2022')]
+sys.argv = [a for a in sys.argv if a not in ('--mingw', '--vs2019', '--vs2022')]
 
 
 # Computes a suitable path prefix to use when building with a given generator.
@@ -314,8 +301,6 @@ def cmake_generator_prefix():
     return '_vs2022'
   if CMAKE_GENERATOR == 'Visual Studio 16':
     return '_vs2019'
-  if CMAKE_GENERATOR == 'Visual Studio 15':
-    return '_vs2017'
   elif CMAKE_GENERATOR == 'MinGW Makefiles':
     return '_mingw'
   # Unix Makefiles do not specify a path prefix for backwards path compatibility
@@ -2685,7 +2670,7 @@ def main(args):
                                   purposes. Default: Enabled
             --disable-assertions: Forces assertions off during the build.
 
-      --vs2017/--vs2019/--vs2022: If building from source, overrides to build
+               --vs2019/--vs2022: If building from source, overrides to build
                                   using the specified compiler. When installing
                                   precompiled packages, this has no effect.
                                   Note: The same compiler specifier must be
@@ -2708,7 +2693,7 @@ def main(args):
 
     if WINDOWS:
       print('''
-   emsdk activate [--permanent] [--system] [--build=type] [--vs2017/--vs2019/--vs2022] <tool/sdk>
+   emsdk activate [--permanent] [--system] [--build=type] [--vs2019/--vs2022] <tool/sdk>
 
                                 - Activates the given tool or SDK in the
                                   environment of the current shell.
@@ -2722,7 +2707,7 @@ def main(args):
                                   (uses Machine environment variables).
 
                                 - If a custom compiler version was used to override
-                                  the compiler to use, pass the same --vs2017/--vs2019/--vs2022
+                                  the compiler to use, pass the same --vs2019/--vs2022
                                   parameter here to choose which version to activate.
 
    emcmdprompt.bat              - Spawns a new command prompt window with the