Intel: Do not use GNU-like flags on Windows

Refactor options out of `Modules/Compiler/Intel-{ASM,C,CXX,Fortran}.cmake`
into a common helper in `Modules/Compiler/Intel.cmake`.  Condition
them to be used only on non-Windows hosts where the Intel compiler
is GNU-like instead of MSVC-like.

Previously this worked only because the options were later overridden
by `Modules/Platform/Windows-Intel*.cmake`, but it is cleaner to not
set the options in the first place.

Modules/Compiler/Intel-ASM.cmake

-set(CMAKE_ASM_VERBOSE_FLAG "-v")
+include(Compiler/Intel)
+__compiler_intel(ASM)
 
-set(CMAKE_ASM_FLAGS_INIT "")
-set(CMAKE_ASM_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_ASM_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-set(CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_ASM_FLAGS_RELWITHDEBINFO_INIT " -DNDEBUG")
 
 if(UNIX)
   set(CMAKE_ASM_SOURCE_FILE_EXTENSIONS s;S)

Modules/Compiler/Intel-C.cmake

-set(CMAKE_C_VERBOSE_FLAG "-v")
+include(Compiler/Intel)
+__compiler_intel(C)
 
-set(CMAKE_C_FLAGS_INIT "")
-set(CMAKE_C_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_C_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-set(CMAKE_C_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-set(CMAKE_C_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_C_FLAGS_RELWITHDEBINFO_INIT " -DNDEBUG")
 
 set(CMAKE_DEPFILE_FLAGS_C "-MD -MT <OBJECT> -MF <DEPFILE>")
 

Modules/Compiler/Intel-CXX.cmake

-set(CMAKE_CXX_VERBOSE_FLAG "-v")
+include(Compiler/Intel)
+__compiler_intel(CXX)
 
-set(CMAKE_CXX_FLAGS_INIT "")
-set(CMAKE_CXX_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_CXX_FLAGS_MINSIZEREL_INIT "-Os -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELEASE_INIT "-O3 -DNDEBUG")
-set(CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT "-O2 -g -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_MINSIZEREL_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELEASE_INIT " -DNDEBUG")
+string(APPEND CMAKE_CXX_FLAGS_RELWITHDEBINFO_INIT " -DNDEBUG")
 
 set(CMAKE_DEPFILE_FLAGS_CXX "-MD -MT <OBJECT> -MF <DEPFILE>")
 

Modules/Compiler/Intel-Fortran.cmake

-set(CMAKE_Fortran_FLAGS_INIT "")
-set(CMAKE_Fortran_FLAGS_DEBUG_INIT "-g")
-set(CMAKE_Fortran_FLAGS_MINSIZEREL_INIT "-Os")
-set(CMAKE_Fortran_FLAGS_RELEASE_INIT "-O3")
-set(CMAKE_Fortran_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+include(Compiler/Intel)
+__compiler_intel(Fortran)
+
 set(CMAKE_Fortran_MODDIR_FLAG "-module ")
-set(CMAKE_Fortran_VERBOSE_FLAG "-v")
 set(CMAKE_Fortran_FORMAT_FIXED_FLAG "-fixed")
 set(CMAKE_Fortran_FORMAT_FREE_FLAG "-free")
 

Modules/Compiler/Intel.cmake

+
+#=============================================================================
+# Copyright 2002-2016 Kitware, Inc.
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.)
+
+# This module is shared by multiple languages; use include blocker.
+if(__COMPILER_INTEL)
+  return()
+endif()
+set(__COMPILER_INTEL 1)
+
+if(CMAKE_HOST_WIN32)
+  # MSVC-like
+  macro(__compiler_intel lang)
+  endmacro()
+else()
+  # GNU-like
+  macro(__compiler_intel lang)
+    set(CMAKE_${lang}_VERBOSE_FLAG "-v")
+
+    set(CMAKE_${lang}_FLAGS_INIT "")
+    set(CMAKE_${lang}_FLAGS_DEBUG_INIT "-g")
+    set(CMAKE_${lang}_FLAGS_MINSIZEREL_INIT "-Os")
+    set(CMAKE_${lang}_FLAGS_RELEASE_INIT "-O3")
+    set(CMAKE_${lang}_FLAGS_RELWITHDEBINFO_INIT "-O2 -g")
+  endmacro()
+endif()