mingw-w64: fix dbghelp on case sensitive systems

- fix dbhelp.h include
- fix dbghelp check and link

CMakeLists.txt

@@ -115,7 +115,7 @@ check_cxx_compiler_flag (-Wunnamed-type-template-args
 check_symbol_exists (snprintf stdio.h HAVE_SNPRINTF)
 
 check_library_exists (unwind get_static_proc_name "" HAVE_LIB_UNWIND)
-check_library_exists (DbgHelp UnDecorateSymbolName "" HAVE_DBGHELP)
+check_library_exists (dbghelp UnDecorateSymbolName "" HAVE_DBGHELP)
 
 find_library (UNWIND_LIBRARY NAMES unwind DOC "unwind library")
 mark_as_advanced (UNWIND_LIBRARY)
@@ -456,7 +456,7 @@ if (UNWIND_LIBRARY)
 endif (UNWIND_LIBRARY)
 
 if (HAVE_DBGHELP)
-   target_link_libraries (glog PUBLIC DbgHelp)
+   target_link_libraries (glog PUBLIC dbghelp)
 endif (HAVE_DBGHELP)
 
 if (HAVE_PTHREAD)

src/demangle.cc

@@ -39,8 +39,8 @@
 #include "demangle.h"
 
 #if defined(OS_WINDOWS)
-#include <DbgHelp.h>
-#pragma comment(lib, "DbgHelp")
+#include <dbghelp.h>
+#pragma comment(lib, "dbghelp")
 #endif
 
 _START_GOOGLE_NAMESPACE_

src/symbolize.cc

@@ -847,10 +847,10 @@ _END_GOOGLE_NAMESPACE_
 #elif defined(OS_WINDOWS) || defined(OS_CYGWIN)
 
 #include <windows.h>
-#include <DbgHelp.h>
+#include <dbghelp.h>
 
 #ifdef _MSC_VER
-#pragma comment(lib, "DbgHelp")
+#pragma comment(lib, "dbghelp")
 #endif
 
 _START_GOOGLE_NAMESPACE_