Use $(CURDIR) instead of ../$(PROJECT) for SHELL_PATH

This fixes the issue where the project name and project directory
differ, and allow us to support directory of the form name-version.

erlang.mk

@@ -1010,7 +1010,7 @@ distclean-relx:
 
 # Configuration.
 
-SHELL_PATH ?= -pa ../$(PROJECT)/ebin $(DEPS_DIR)/*/ebin
+SHELL_PATH ?= -pa $(CURDIR)/ebin $(DEPS_DIR)/*/ebin
 SHELL_OPTS ?=
 
 ALL_SHELL_DEPS_DIRS = $(addprefix $(DEPS_DIR)/,$(SHELL_DEPS))

plugins/shell.mk

@@ -5,7 +5,7 @@
 
 # Configuration.
 
-SHELL_PATH ?= -pa ../$(PROJECT)/ebin $(DEPS_DIR)/*/ebin
+SHELL_PATH ?= -pa $(CURDIR)/ebin $(DEPS_DIR)/*/ebin
 SHELL_OPTS ?=
 
 ALL_SHELL_DEPS_DIRS = $(addprefix $(DEPS_DIR)/,$(SHELL_DEPS))