Eina log: flush stderr on mintty-based terminals
Summary: on those terminal, stderr is never flushed, so errors messages are not displayed when, for example, the app crashes
Test Plan:
test program :
```#include <Eina.h>
#define ERR(...) EINA_LOG_DOM_ERR(log_dom, __VA_ARGS__)
int main()
{
int log_dom = -1;
eina_init();
log_dom = eina_log_domain_register("eet", EINA_COLOR_CYAN);
if (log_dom < 0)
{
printf("error register\n");
return 0;
}
ERR("an error.");
while (1)
{
}
return 0;
}
```
without the patch, nothing is displayed, even after a Ctrl-C to finish the program
with the patch, the error message is displayed
Reviewers: raster
Reviewed By: raster
Subscribers: cedric, #reviewers, #committers
Tags: #efl
Differential Revision: https://phab.enlightenment.org/D12058