modify sed commands to handle non-GNU and GNU od

Another one-line fix :) tested on solaris, seems to generate identical browse_py.h
Looking at this, the new line matches space or tab followed by a single digit, while a line of output from `od` looks like this for me:

           23  20  53  77  61  6c  6c  6f  77  20  63  6f  6e  73  6f  6c

So this breaks things for me over here, as the preceding line now gets converted to

    "          \x23 \x20 \x53 \x77 \x61 \x6c \x6c \x6f \x77 \x20 \x63 \x6f \x6e \x73 \x6f \x6c"

instead of

    "\x23\x20\x53\x77\x61\x6c\x6c\x6f\x77\x20\x63\x6f\x6e\x73\x6f\x6c"

previously. Does just changing `s| ||g` to `s|[ \t]||g` make things go for you? (You can test by running `./ninja -t browse ninja` after building ninja.)