osx: delay version computation on macOS builds
Before this patch, HGVER would be evaluated at the beginning of the make
execution, and would be unset because build/mercurial/ doesn't exist yet
at that point. Now we compute the version after the `make install` run
has completed.
This is backported to stable from
8626b44516c1, but that revision had an
error in the shell invocation syntax.
$ hg init
$ $PYTHON -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
$ hg ci -Ama -d '1 0'
adding a
$ echo clean diff >> a
$ hg ci -mb -d '2 0'
$ hg diff -r0 -r1
diff -r 107ba6f817b5 -r 310ce7989cdc a
--- a/a Thu Jan 01 00:00:01 1970 +0000
+++ b/a Thu Jan 01 00:00:02 1970 +0000
@@ -1,2 +1,3 @@
confuse str.splitlines
embedded\r (no-eol) (esc)
newline
+clean diff