Disable `conversion` warning on win32/gnu-mingw (#4516)
Disable `conversion` warning on win32/gnu-mingw (#4516)

It's a mingw-runtime issue, but we disable conversion warning on win32/gnu-mingw
for getting jerryscript compile with mingw first.
The bug url are: https://sourceforge.net/p/mingw-w64/bugs/874/

JerryScript-DCO-1.0-Signed-off-by: Yonggang Luo luoyonggang@gmail.com
jerryscript-project/jerryscript,bzsolt/jerryscript,robertsipka/jerryscript,zherczeg/jerryscript,robertsipka/jerryscript,dbatyai/jerryscript,dbatyai/jerryscript,jerryscript-project/jerryscript,dbatyai/jerryscript,zherczeg/jerryscript,robertsipka/jerryscript,jerryscript-project/jerryscript,robertsipka/jerryscript,robertsipka/jerryscript,zherczeg/jerryscript,bzsolt/jerryscript,bzsolt/jerryscript,bzsolt/jerryscript,dbatyai/jerryscript,bzsolt/jerryscript,zherczeg/jerryscript,dbatyai/jerryscript,jerryscript-project/jerryscript,zherczeg/jerryscript,jerryscript-project/jerryscript,robertsipka/jerryscript