test-share: Solaris sed can't handle never-ending lines

tests/test-share

@@ -18,8 +18,8 b' cd repo2'
 [ -d .hg/store ] \
   && echo "fail: .hg/store should not exist" \
   || echo "pass: .hg/store does not exist"
-# sed appends a newline to the stream if none, GNU sed does not
-sed "s:$HGTMP:*HGTMP*:" .hg/sharedpath | tr -d '\n'; echo
+# Some sed versions appends newline, some don't, and some just fails
+(cat .hg/sharedpath; echo) | head -n1 | sed "s:$HGTMP:*HGTMP*:"
 
 echo % commit in shared clone
 echo a >> a