don't pass -fstack-clash-protection to mingw when building onetbb

GCC 10.4 aborts compiling oneTBB's task_dispatcher.h with the flag on:

  internal compiler error: in seh_emit_stackalloc, at config/i386/winnt.c:1056
    370 |                 do_throw_noexcept([] { throw; });

a known GCC defect on mingw's SEH targets. It is a hardening flag rather
than a correctness one, so leave it off there.

Also fold the earlier /dev/null fix into a single patches/mingw_gnu_cmake.diff,
as both make oneTBB's GNU.cmake usable for a native mingw build.

Author: kevinushey

patches/mingw_devnull.diff patches/mingw_gnu_cmake.diffpatches/mingw_devnull.diff renamed to patches/mingw_gnu_cmake.diff

@@ -1,5 +1,5 @@
 diff --git a/src/tbb/cmake/compilers/GNU.cmake b/src/tbb/cmake/compilers/GNU.cmake
-index cf6d8bdb..4c5e43a9 100644
+index cf6d8bdb..bc86acc1 100644
 --- a/src/tbb/cmake/compilers/GNU.cmake
 +++ b/src/tbb/cmake/compilers/GNU.cmake
 @@ -47,19 +47,42 @@ endif()
@@ -46,3 +46,19 @@ index cf6d8bdb..4c5e43a9 100644
  message(TRACE "Extracted GNU assembler version: major=${_tbb_gnu_asm_major_version} minor=${_tbb_gnu_asm_minor_version}")
 
  math(EXPR _tbb_gnu_asm_version_number  "${_tbb_gnu_asm_major_version} * 1000 + ${_tbb_gnu_asm_minor_version}")
+@@ -81,7 +104,14 @@ endif()
+ if (NOT ${CMAKE_CXX_COMPILER_ID} STREQUAL Intel)
+     # gcc 6.0 and later have -flifetime-dse option that controls elimination of stores done outside the object lifetime
+     set(TBB_DSE_FLAG $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},6.0>>:-flifetime-dse=1>)
+-    set(TBB_COMMON_COMPILE_FLAGS ${TBB_COMMON_COMPILE_FLAGS} $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},8.0>>:-fstack-clash-protection>)
++
++    # -fstack-clash-protection is broken on mingw's SEH targets: compiling
++    # task_dispatcher.h makes GCC 10 abort with "internal compiler error: in
++    # seh_emit_stackalloc, at config/i386/winnt.c". It is a hardening flag
++    # rather than a correctness one, so simply leave it off there.
++    if (NOT MINGW)
++        set(TBB_COMMON_COMPILE_FLAGS ${TBB_COMMON_COMPILE_FLAGS} $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},8.0>>:-fstack-clash-protection>)
++    endif()
+ 
+     # Suppress GCC 12.x-13.x warning here that to_wait_node(n)->my_is_in_list might have size 0
+     set(TBB_COMMON_LINK_FLAGS ${TBB_COMMON_LINK_FLAGS} $<$<AND:$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},12.0>>,$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},14.0>>:-Wno-stringop-overflow>)

src/tbb/cmake/compilers/GNU.cmake

@@ -104,7 +104,14 @@ endif()
 if (NOT ${CMAKE_CXX_COMPILER_ID} STREQUAL Intel)
     # gcc 6.0 and later have -flifetime-dse option that controls elimination of stores done outside the object lifetime
     set(TBB_DSE_FLAG $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},6.0>>:-flifetime-dse=1>)
-    set(TBB_COMMON_COMPILE_FLAGS ${TBB_COMMON_COMPILE_FLAGS} $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},8.0>>:-fstack-clash-protection>)
+
+    # -fstack-clash-protection is broken on mingw's SEH targets: compiling
+    # task_dispatcher.h makes GCC 10 abort with "internal compiler error: in
+    # seh_emit_stackalloc, at config/i386/winnt.c". It is a hardening flag
+    # rather than a correctness one, so simply leave it off there.
+    if (NOT MINGW)
+        set(TBB_COMMON_COMPILE_FLAGS ${TBB_COMMON_COMPILE_FLAGS} $<$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},8.0>>:-fstack-clash-protection>)
+    endif()
 
     # Suppress GCC 12.x-13.x warning here that to_wait_node(n)->my_is_in_list might have size 0
     set(TBB_COMMON_LINK_FLAGS ${TBB_COMMON_LINK_FLAGS} $<$<AND:$<NOT:$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},12.0>>,$<VERSION_LESS:${CMAKE_CXX_COMPILER_VERSION},14.0>>:-Wno-stringop-overflow>)