Build: Don't omit lzma_cputhreads() unless using --disable-threads.

Previously it was omitted if encoders were disabled
with --disable-encoders. It didn't make sense and
it also broke the build.

src/liblzma/common/Makefile.inc

@@ -21,6 +21,10 @@ liblzma_la_SOURCES += \
 	common/stream_flags_common.h \
 	common/vli_size.c
 
+if COND_THREADS
+liblzma_la_SOURCES += common/hardware_cputhreads.c
+endif
+
 if COND_MAIN_ENCODER
 liblzma_la_SOURCES += \
 	common/alone_encoder.c \
@@ -45,7 +49,6 @@ liblzma_la_SOURCES += \
 
 if COND_THREADS
 liblzma_la_SOURCES += \
-	common/hardware_cputhreads.c \
 	common/outqueue.c \
 	common/outqueue.h \
 	common/stream_encoder_mt.c