Fixes for VS preview (#45902)

* Fixes for VS preview

Stop using c++latest and designated initializers for Windows crossdac
Disable warning about overriding /TP with /TC

Author: sdmaclea

src/coreclr/pal/src/exception/remote-unwind.cpp

@@ -1975,18 +1975,24 @@ put_unwind_info(unw_addr_space_t as, unw_proc_info_t *pip, void *arg)
 {
 }
 
-static unw_accessors_t unwind_accessors =
+static unw_accessors_t init_unwind_accessors()
 {
-    .find_proc_info = find_proc_info,
-    .put_unwind_info = put_unwind_info,
-    .get_dyn_info_list_addr = get_dyn_info_list_addr,
-    .access_mem = access_mem,
-    .access_reg = access_reg,
-    .access_fpreg = access_fpreg,
-    .resume = resume,
-    .get_proc_name = get_proc_name
+    unw_accessors_t a = {0};
+
+    a.find_proc_info = find_proc_info;
+    a.put_unwind_info = put_unwind_info;
+    a.get_dyn_info_list_addr = get_dyn_info_list_addr;
+    a.access_mem = access_mem;
+    a.access_reg = access_reg;
+    a.access_fpreg = access_fpreg;
+    a.resume = resume;
+    a.get_proc_name = get_proc_name;
+
+    return a;
 };
 
+static unw_accessors_t unwind_accessors = init_unwind_accessors();
+
 /*++
 Function:
     PAL_VirtualUnwindOutOfProc

src/coreclr/pal/src/libunwind/CMakeLists.txt

@@ -124,7 +124,6 @@ if(CLR_CMAKE_HOST_WIN32)
     endif ()
 
     # Assume we are using default MSVC compiler
-    add_compile_options(/std:c++latest)
     add_compile_options(/TC) # compile all files as C
     add_compile_options(/permissive-)
 
@@ -148,6 +147,8 @@ if(CLR_CMAKE_HOST_WIN32)
     add_compile_options(-wd4311) # pointer truncation from 'unw_word_t *' to 'long'
     add_compile_options(-wd4475) # 'fprintf' : length modifier 'L' cannot be used
     add_compile_options(-wd4477) # fprintf argument type
+
+    add_compile_options(-wd9025) # overriding '/TP' with '/TC'
 endif (CLR_CMAKE_HOST_WIN32)
 
 if(CLR_CMAKE_TARGET_ARCH_ARM)