As I mentioned in a previous message, it looks like UnxUtils is not installed properly in your system. Bison.exe is not finding "bison.simple" therefore the error you get. In my system I have "C:\usr\local\wbin\bison.exe" and "C:\usr\local\share\bison.simple". Alternatively you could just copy "bison.simple" into "C:\usr\local". Everything is explained in section 2.4.5 of the sdcc manual.
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Problem : Performing custom build step on .\SDCC.y
/usr/local/bison.simple: no such file on directory bison:
error executing c:\window\system32\cmd.exe
As I mentioned in a previous message, it looks like UnxUtils is not installed properly in your system. Bison.exe is not finding "bison.simple" therefore the error you get. In my system I have "C:\usr\local\wbin\bison.exe" and "C:\usr\local\share\bison.simple". Alternatively you could just copy "bison.simple" into "C:\usr\local". Everything is explained in section 2.4.5 of the sdcc manual.