Use printf %s instead of echo -n in build script

According to POSIX, the behavior of `echo -n` is "implementation
defined". So we can't guarantee that it gives the same result
everywhere.

See also:
* http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html
* http://unix.stackexchange.com/q/65803/9814

Author: lambda-fairy

mk/main.mk

@@ -22,7 +22,7 @@ CFG_PRERELEASE_VERSION=.1
 
 # Append a version-dependent hash to each library, so we can install different
 # versions in the same place
-CFG_FILENAME_EXTRA=$(shell echo -n $(CFG_RELEASE) | $(CFG_HASH_COMMAND))
+CFG_FILENAME_EXTRA=$(shell printf '%s' $(CFG_RELEASE) | $(CFG_HASH_COMMAND))
 
 ifeq ($(CFG_RELEASE_CHANNEL),stable)
 # This is the normal semver version string, e.g. "0.12.0", "0.12.0-nightly"