replace usages of 'wc' in test scripts with simpler ways

[fogti]

rust/src/test/run-make-fulldeps/target-cpu-native/Makefile

Line 11 in 730d6df

if [ "$$(wc -c $(TMPDIR)/out.log | cut -d' ' -f 1)" = "0" ]; then \

see also: #53642 (comment)
As noted above, the snip [ $(wc -c file | cut -d' ' -f1) == 0 ] should be replaced with ! [ -s file ] which should make such scripts more portable.
other locations of this are easily found with: https://github.com/rust-lang/rust/search?q=wc (only the = "0" or -eq 0 or such usages are interesting)