diff -upr thunderbird-59.0b1.orig/mozilla/config/baseconfig.mk
thunderbird-59.0b1/mozilla/config/baseconfig.mk
--- thunderbird-59.0b1.orig/mozilla/config/baseconfig.mk
2018-02-03 21:40:48.387811590 +0300
+++ thunderbird-59.0b1/mozilla/config/baseconfig.mk        2018-02-03
21:40:17.997729401 +0300
@@ -2,7 +2,7 @@
 # directly in python/mozbuild/mozbuild/base.py for gmake validation.
 # We thus use INCLUDED_AUTOCONF_MK to enable/disable some parts
depending
 # whether a normal build is happening or whether the check is
running.
-installdir = $(libdir)/$(MOZ_APP_NAME)
+installdir = $(libdir)/$(MOZ_APP_NAME)-beta
 ifeq (.,$(DEPTH))
 DIST = dist
 else