Simplify the Makefile to fix MSVC build. Mkvcbuild does not support variables

expansion in makefiles, so the build failed on the Windows systems.

Author: rzharkov

.gitignore

@@ -2,7 +2,6 @@
 *.o
 *.so
 /results
-*pg_wait_sampling--1.1.sql
 .log
 Dockerfile
 /log/

Makefile

@@ -4,14 +4,11 @@ MODULE_big = pg_wait_sampling
 OBJS = pg_wait_sampling.o collector.o compat.o
 
 EXTENSION = pg_wait_sampling
-EXTVERSION = 1.1
-DATA_built = pg_wait_sampling--$(EXTVERSION).sql
-DATA = pg_wait_sampling--1.0--1.1.sql
+DATA = pg_wait_sampling--1.1.sql pg_wait_sampling--1.0--1.1.sql
 
 REGRESS = load queries
 
 EXTRA_REGRESS_OPTS=--temp-config=$(top_srcdir)/$(subdir)/conf.add
-EXTRA_CLEAN = pg_wait_sampling--$(EXTVERSION).sql
 
 ifdef USE_PGXS
 PG_CONFIG = pg_config
@@ -24,9 +21,6 @@ include $(top_builddir)/src/Makefile.global
 include $(top_srcdir)/contrib/contrib-global.mk
 endif
 
-$(EXTENSION)--$(EXTVERSION).sql: setup.sql
-	cat $^ > $@
-
 # Prepare the package for PGXN submission
 package: dist .git
 	$(eval DISTVERSION := $(shell git tag -l | tail -n 1 | cut -d 'v' -f 2))