use lowercase --define switches (#17283)

lib/system/arithm.nim

@@ -155,7 +155,7 @@ proc absInt(a: int): int {.compilerproc, inline.} =
   raiseOverflow()
 
 const
-  asmVersion = defined(I386) and (defined(vcc) or defined(wcc) or
+  asmVersion = defined(i386) and (defined(vcc) or defined(wcc) or
                defined(dmc) or defined(gcc) or defined(llvm_gcc))
     # my Version of Borland C++Builder does not have
     # tasm32, which is needed for assembler blocks

lib/system/io.nim

@@ -143,13 +143,13 @@ proc raiseEOF() {.noinline, noreturn.} =
 
 proc strerror(errnum: cint): cstring {.importc, header: "<string.h>".}
 
-when not defined(NimScript):
+when not defined(nimscript):
   var
     errno {.importc, header: "<errno.h>".}: cint ## error variable
     EINTR {.importc: "EINTR", header: "<errno.h>".}: cint
 
 proc checkErr(f: File) =
-  when not defined(NimScript):
+  when not defined(nimscript):
     if c_ferror(f) != 0:
       let msg = "errno: " & $errno & " `" & $strerror(errno) & "`"
       c_clearerr(f)
@@ -452,7 +452,7 @@ proc readLine*(f: File, line: var string): bool {.tags: [ReadIOEffect],
       # likely other io procs need this for correctness.
       fgetsSuccess = c_fgets(addr line[pos], sp.cint, f) != nil
       if fgetsSuccess: break
-      when not defined(NimScript):
+      when not defined(nimscript):
         if errno == EINTR:
           errno = 0
           c_clearerr(f)

lib/system/syslocks.nim

@@ -11,7 +11,7 @@
 
 {.push stackTrace: off.}
 
-when defined(Windows):
+when defined(windows):
   type
     Handle = int