add back building boot files with extra defines but use explicitly specified values instead of generic NASMFLAGS so flags used for other assembly files does not effect building

boot/makefile

@@ -8,22 +8,22 @@
 production:     fat12com.bin fat16com.bin fat32chs.bin fat32lba.bin oemfat12.bin oemfat16.bin
 
 fat12com.bin:    boot.asm
-		$(NASM) -dISFAT12 boot.asm -l$*.lst -ofat12com.bin
+		$(NASM) -dISFAT12 $(NASMBOOTFLAGS) boot.asm -l$*.lst -ofat12com.bin
 
 fat16com.bin:    boot.asm
-		$(NASM) -dISFAT16 boot.asm -l$*.lst -ofat16com.bin
+		$(NASM) -dISFAT16 $(NASMBOOTFLAGS) boot.asm -l$*.lst -ofat16com.bin
 
 fat32chs.bin:    boot32.asm
-		$(NASM) boot32.asm -l$*.lst -ofat32chs.bin
+		$(NASM) $(NASMBOOTFLAGS) boot32.asm -l$*.lst -ofat32chs.bin
 
 fat32lba.bin:    boot32lb.asm
-		$(NASM) boot32lb.asm -l$*.lst -ofat32lba.bin
+		$(NASM) $(NASMBOOTFLAGS) boot32lb.asm -l$*.lst -ofat32lba.bin
 
 oemfat12.bin:   oemboot.asm
-		$(NASM) -dISFAT12 oemboot.asm -l$*.lst -ooemfat12.bin
+		$(NASM) -dISFAT12 $(NASMBOOTFLAGS) oemboot.asm -l$*.lst -ooemfat12.bin
 
 oemfat16.bin:   oemboot.asm
-		$(NASM) -dISFAT16 oemboot.asm -l$*.lst -ooemfat16.bin
+		$(NASM) -dISFAT16 $(NASMBOOTFLAGS) oemboot.asm -l$*.lst -ooemfat16.bin
 
 clobber:        clean
 		-$(RM) *.bin status.me

build.bat

@@ -163,6 +163,8 @@ if "%1" == "" goto abort
 if "%2" == "/V" goto :setDefineWithValue
 set ALLCFLAGS=%ALLCFLAGS% -D%1
 set NASMFLAGS=%NASMFLAGS% -D%1
+REM $(NASMBOOTFLAGS) are extra flags only used when building boot sectors
+set NASMBOOTFLAGS=%NASMBOOTFLAGS% -d%1
 goto nextOption
 
 :setDefineWithValue

default.bat

@@ -80,6 +80,7 @@ set BC5_BASE=
 set MS_BASE=
 set XNASM=
 set NASMFLAGS=
+set NASMBOOTFLAGS=
 set XUPX=
 set UPXOPT=
 set LOADSEG=