[log] Change log file mode to wb+/w+

For testing log file parsing from JavaScript we need to be able to
read open log files directly. This makes the default log file mode
consistent with the temporary one.

Bug: v8:1064
Change-Id: Ic77ba6864efe633e54792fc683edc2fe07af4cd5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2400993Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69783}

src/base/platform/platform-posix.cc

@@ -679,9 +679,7 @@ FILE* OS::OpenTemporaryFile() {
   return tmpfile();
 }
 
-
-const char* const OS::LogFileOpenMode = "w";
-
+const char* const OS::LogFileOpenMode = "w+";
 
 void OS::Print(const char* format, ...) {
   va_list args;

src/base/platform/platform-win32.cc

@@ -603,8 +603,7 @@ FILE* OS::OpenTemporaryFile() {
 
 
 // Open log file in binary mode to avoid /n -> /r/n conversion.
-const char* const OS::LogFileOpenMode = "wb";
-
+const char* const OS::LogFileOpenMode = "wb+";
 
 // Print (debug) message to console.
 void OS::Print(const char* format, ...) {