mingw: Fix number of exponent digits in floating point formatting

By default mingw outputs 3 digits instead of the standard 2 so all float
tests using printf fail. Using setenv at the start of the program fixes this.
To accomodate calling platform specific initialization a
MICROPY_MAIN_INIT_FUNC macro is used which is called in mp_init()

1 files changed, 5 insertions, 0 deletions

diff --git a/windows/init.c b/windows/init.c
new file mode 100644
index 0000000000..78b8738f77
--- /dev/null
+++ b/windows/init.c
@@ -0,0 +1,5 @@
+#include <stdlib.h>
+
+void init() {
+    putenv("PRINTF_EXPONENT_DIGITS=2");
+}