btrfs-progs: don't link binaries to a dynamic library

Linking 'btrfs' and other binaries against the dynamic library makes it
tedious to use directly from the git repo. This is useful for testing
various fixes, but now it'd need to also set LD_LIBRARY_PATH or install
the library to a known path.

Add a target for static library and use it for linking, the dynamic
library is to be used by external users.

Signed-off-by: David Sterba <dsterba@suse.cz>

Makefile

@@ -1,5 +1,6 @@
 CC = gcc
 LN = ln
+AR = ar
 AM_CFLAGS = -Wall -D_FILE_OFFSET_BITS=64 -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -DBTRFS_FLAT_INCLUDES -fPIC
 CFLAGS = -g -O1
 objects = ctree.o disk-io.o radix-tree.o extent-tree.o print-tree.o \
@@ -26,7 +27,7 @@ bindir = $(prefix)/bin
 lib_LIBS = -luuid -lblkid -lm -lz -L.
 libdir ?= $(prefix)/lib
 incdir = $(prefix)/include/btrfs
-LIBS = $(lib_LIBS) -lbtrfs
+LIBS = $(lib_LIBS) $(libs_static)
 
 ifeq ("$(origin V)", "command line")
   BUILD_VERBOSE = $(V)
@@ -57,7 +58,9 @@ STATIC_CFLAGS = $(CFLAGS) -ffunction-sections -fdata-sections
 STATIC_LDFLAGS = -static -Wl,--gc-sections
 STATIC_LIBS = $(LIBS) -lpthread
 
-libs = libbtrfs.so.0.1
+libs_shared = libbtrfs.so.0.1
+libs_static = libbtrfs.a
+libs = $(libs_shared) $(libs_static)
 lib_links = libbtrfs.so.0 libbtrfs.so
 headers = $(libbtrfs_headers)
 
@@ -88,10 +91,14 @@ static: version.h $(libs) btrfs.static
 version.h:
 	$(Q)bash version.sh
 
-$(libs): $(libbtrfs_objects) $(lib_links) send.h
+$(libs_shared): $(libbtrfs_objects) $(lib_links) send.h
 	@echo "    [LD]     $@"
 	$(Q)$(CC) $(CFLAGS) $(libbtrfs_objects) $(lib_LIBS) -shared -Wl,-soname,libbtrfs.so -o libbtrfs.so.0.1
 
+$(libs_static): $(libbtrfs_objects)
+	@echo "    [AR]     $@"
+	$(Q)$(AR) cru libbtrfs.a $(libbtrfs_objects)
+
 $(lib_links):
 	@echo "    [LN]     $@"
 	$(Q)$(LN) -sf libbtrfs.so.0.1 libbtrfs.so.0