CMakeParseImplicitLinkInfo: Exclude LLVMFlang program entry point for MSVC

As of llvm-project `main` branch commit `86accd4e03` (2023-12-04),
LLVMFlang 18.0.0, when used to drive linking an executable, emits a MSVC
linker flag to use all object files from the `Fortran_main` library.
These object files are meant for use when linking the program entry
point, and so are not implicit link dependencies of Fortran libraries.

Modules/CMakeParseImplicitLinkInfo.cmake

@@ -163,6 +163,8 @@ function(cmake_parse_implicit_link_info2 text log_var obj_regex)
           string(APPEND log "    arg [${arg}] ==> ignore MSVC cl option\n")
         elseif(is_msvc AND "${arg}" MATCHES "^[-/][Ii][Mm][Pp][Ll][Ii][Bb]:")
           string(APPEND log "    arg [${arg}] ==> ignore MSVC link option\n")
+        elseif(is_msvc AND "${arg}" MATCHES "^[-/][Ww][Hh][Oo][Ll][Ee][Aa][Rr][Cc][Hh][Ii][Vv][Ee]:Fortran_main")
+          string(APPEND log "    arg [${arg}] ==> ignore LLVMFlang program entry point\n")
         elseif(is_msvc AND "${arg}" MATCHES "^(.*\\.[Ll][Ii][Bb])$")
           if(EXTRA_PARSE_COMPUTE_IMPLICIT_LIBS)
             set(lib "${CMAKE_MATCH_1}")

Tests/RunCMake/ParseImplicitData/windows_x86_64-Fortran-LLVMFlang-18.0.0-MSVC.input

@@ -0,0 +1,20 @@
+CMAKE_LANG=Fortran
+CMAKE_LINKER=
+CMAKE_Fortran_COMPILER_ABI=
+CMAKE_Fortran_COMPILER_AR=
+CMAKE_Fortran_COMPILER_ARCHITECTURE_ID=x64
+CMAKE_Fortran_COMPILER_EXTERNAL_TOOLCHAIN=
+CMAKE_Fortran_COMPILER_ID=LLVMFlang
+CMAKE_Fortran_COMPILER_LAUNCHER=
+CMAKE_Fortran_COMPILER_LOADED=1
+CMAKE_Fortran_COMPILER_RANLIB=
+CMAKE_Fortran_COMPILER_TARGET=
+CMAKE_Fortran_COMPILER_VERSION=18.0.0
+CMAKE_Fortran_COMPILER_VERSION_INTERAL=
+CMAKE_Fortran_SIMULATE_ID=MSVC
+flang-new version 18.0.0
+Target: x86_64-pc-windows-msvc
+Thread model: posix
+InstalledDir: C:\DoesNotExist\LLVM\bin
+ "C:\\DoesNotExist\\LLVM\\bin\\flang-new" -fc1 -triple x86_64-pc-windows-msvc19.36.32543 -emit-obj -mrelocation-model pic -pic-level 2 -target-cpu x86-64 --dependent-lib=clang_rt.builtins-x86_64.lib -D_MT --dependent-lib=libcmt --dependent-lib=Fortran_main.static.lib --dependent-lib=FortranRuntime.static.lib --dependent-lib=FortranDecimal.static.lib -D_MSC_VER=1936 -D_MSC_FULL_VER=193632543 -D_WIN32 -D_M_X64=100 -mframe-pointer=none -o "C:\\DoesNotExist\\Temp\\CMakeFortranCompilerABI-e91f95.o" -x f95-cpp-input CMakeFortranCompilerABI.F
+ "C:\\Program Files\\Microsoft Visual Studio\\2022\\Professional\\VC\\Tools\\MSVC\\14.36.32532\\bin\\Hostx64\\x64\\link.exe" -out:a.exe "-libpath:C:\\DoesNotExist\\LLVM\\lib" /WHOLEARCHIVE:Fortran_main.static.lib /subsystem:console "-libpath:C:\\DoesNotExist\\LLVM\\lib\\clang\\18\\lib\\windows" -nologo "C:\\DoesNotExist\\Temp\\CMakeFortranCompilerABI-e91f95.o"

Tests/RunCMake/ParseImplicitLinkInfo/ParseImplicitLinkInfo.cmake

@@ -43,6 +43,7 @@ set(targets
   openbsd-C-Clang-5.0.1 openbsd-CXX-Clang-5.0.1
   sunos-C-SunPro-5.13.0 sunos-CXX-SunPro-5.13.0 sunos-Fortran-SunPro-8.8.0
   windows_x86_64-C-Clang-17.0.1-MSVC windows_x86_64-CXX-Clang-17.0.1-MSVC windows_x86_64-Fortran-LLVMFlang-17.0.1-MSVC
+  windows_x86_64-Fortran-LLVMFlang-18.0.0-MSVC
   windows_arm64-C-Clang-17.0.1-MSVC windows_arm64-CXX-Clang-17.0.1-MSVC windows_arm64-Fortran-LLVMFlang-17.0.1-MSVC
   )
 

Tests/RunCMake/ParseImplicitLinkInfo/results/windows_x86_64-Fortran-LLVMFlang-18.0.0-MSVC.output

@@ -0,0 +1,2 @@
+libs=
+dirs=C:/DoesNotExist/LLVM/lib;C:/DoesNotExist/LLVM/lib/clang/18/lib/windows