Thanks for trying, Carlos.
I found a fix suggested on another post but I have no idea how to implement it. The fix is adding
CFLAGS= -g -Wall -O2 #-m64 #-arch ppc
DFLAGS= -D_FILE_OFFSET_BITS=64 -D_USE_KNETFILE -D_CURSES_LIB=1 -Dexpl=exp -Dlogl=log
to Makefile. I found three makefiles and none of them had any CFLAGS in the file. Is it even possible to install samtools on windows?