tools/power/cpupower: Support building libcpupower statically

The cpupower Makefile built and installed libcpupower as a shared
library (libcpupower.so) without passing `STATIC=true`, but did not
build a static version of the library even with `STATIC=true`. (Only the
programs were static). Thus, out-of-tree programs using libcpupower
were unable to link statically against the library without having access
to intermediate object files produced during the build.

This fixes that situation by ensuring that libcpupower.a is built and
installed when `STATIC=true` is specified.

Link: https://lore.kernel.org/r/x7geegquiks3zndiavw2arihdc2rk7e2dx3lk7yxkewqii6zpg@tzjijqxyzwmu
Signed-off-by: Zuo An <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/power/cpupower/Makefile

···
 # cpufreq-bench benchmarking tool
 CPUFREQ_BENCH ?= true
 
-# Do not build libraries, but build the code in statically
-# Libraries are still built, otherwise the Makefile code would
-# be rather ugly.
+# Build the code, including libraries, statically.
 export STATIC ?= false
 
 # Prefix to the directories we're installing to
···
 	$(ECHO) "  CC      " $@
 	$(QUIET) $(CC) $(CFLAGS) -fPIC -o $@ -c lib/$*.c
 
-$(OUTPUT)libcpupower.so.$(LIB_VER): $(LIB_OBJS)
+ifeq ($(strip $(STATIC)),true)
+LIBCPUPOWER := libcpupower.a
+else
+LIBCPUPOWER := libcpupower.so.$(LIB_VER)
+endif
+
+$(OUTPUT)$(LIBCPUPOWER): $(LIB_OBJS)
+ifeq ($(strip $(STATIC)),true)
+	$(ECHO) "  AR      " $@
+	$(QUIET) $(AR) rcs $@ $(LIB_OBJS)
+else
 	$(ECHO) "  LD      " $@
 	$(QUIET) $(CC) -shared $(CFLAGS) $(LDFLAGS) -o $@ \
 		-Wl,-soname,libcpupower.so.$(LIB_MAJ) $(LIB_OBJS)
 	@ln -sf $(@F) $(OUTPUT)libcpupower.so
 	@ln -sf $(@F) $(OUTPUT)libcpupower.so.$(LIB_MAJ)
+endif
 
-libcpupower: $(OUTPUT)libcpupower.so.$(LIB_VER)
+libcpupower: $(OUTPUT)$(LIBCPUPOWER)
 
 # Let all .o files depend on its .c file and all headers
 # Might be worth to put this into utils/Makefile at some point of time
···
 	$(ECHO) "  CC      " $@
 	$(QUIET) $(CC) $(CFLAGS) -I./lib -I ./utils -o $@ -c $*.c
 
-$(OUTPUT)cpupower: $(UTIL_OBJS) $(OUTPUT)libcpupower.so.$(LIB_VER)
+$(OUTPUT)cpupower: $(UTIL_OBJS) $(OUTPUT)$(LIBCPUPOWER)
 	$(ECHO) "  CC      " $@
 ifeq ($(strip $(STATIC)),true)
 	$(QUIET) $(CC) $(CFLAGS) $(LDFLAGS) $(UTIL_OBJS) -lrt -lpci -L$(OUTPUT) -o $@
···
 	done;
 endif
 
-compile-bench: $(OUTPUT)libcpupower.so.$(LIB_VER)
+compile-bench: $(OUTPUT)$(LIBCPUPOWER)
 	@V=$(V) confdir=$(confdir) $(MAKE) -C bench O=$(OUTPUT)
 
 # we compile into subdirectories. if the target directory is not the
···
 	-find $(OUTPUT) \( -not -type d \) -and \( -name '*~' -o -name '*.[oas]' \) -type f -print \
 	 | xargs rm -f
 	-rm -f $(OUTPUT)cpupower
+	-rm -f $(OUTPUT)libcpupower.a
 	-rm -f $(OUTPUT)libcpupower.so*
 	-rm -rf $(OUTPUT)po/*.gmo
 	-rm -rf $(OUTPUT)po/*.pot
···
 
 install-lib: libcpupower
 	$(INSTALL) -d $(DESTDIR)${libdir}
+ifeq ($(strip $(STATIC)),true)
+	$(CP) $(OUTPUT)libcpupower.a $(DESTDIR)${libdir}/
+else
 	$(CP) $(OUTPUT)libcpupower.so* $(DESTDIR)${libdir}/
+endif
 	$(INSTALL) -d $(DESTDIR)${includedir}
 	$(INSTALL_DATA) lib/cpufreq.h $(DESTDIR)${includedir}/cpufreq.h
 	$(INSTALL_DATA) lib/cpuidle.h $(DESTDIR)${includedir}/cpuidle.h
···
 	@#DESTDIR must be set from outside to survive
 	@sbindir=$(sbindir) bindir=$(bindir) docdir=$(docdir) confdir=$(confdir) $(MAKE) -C bench O=$(OUTPUT) install
 
-ifeq ($(strip $(STATIC)),true)
-install: all install-tools install-man $(INSTALL_NLS) $(INSTALL_BENCH)
-else
 install: all install-lib install-tools install-man $(INSTALL_NLS) $(INSTALL_BENCH)
-endif
 
 uninstall:
 	- rm -f $(DESTDIR)${libdir}/libcpupower.*