tools/build: Add libcpupower dependency detection

Add the ability to detect the presence of libcpupower on a system to
the Makefiles in tools/build.

Link: https://lore.kernel.org/[e-mail]
Signed-off-by: Tomas Glozar <[e-mail]>
Signed-off-by: Steven Rostedt (Google) <[e-mail]>

tools/build/Makefile.feature

···
         libslang-include-subdir         \
         libtraceevent                   \
         libtracefs                      \
+        libcpupower                     \
         libcrypto                       \
         libunwind                       \
         pthread-attr-setaffinity-np     \

tools/build/feature/Makefile

···
          test-libslang.bin                      \
          test-libslang-include-subdir.bin       \
          test-libtraceevent.bin                 \
+         test-libcpupower.bin                   \
          test-libtracefs.bin                    \
          test-libcrypto.bin                     \
          test-libunwind.bin                     \
···
 
 $(OUTPUT)test-libtraceevent.bin:
 	$(BUILD) -ltraceevent
+
+$(OUTPUT)test-libcpupower.bin:
+	$(BUILD) -lcpupower
 
 $(OUTPUT)test-libtracefs.bin:
 	 $(BUILD) $(shell $(PKG_CONFIG) --cflags libtracefs 2>/dev/null) -ltracefs

tools/build/feature/test-libcpupower.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include <cpuidle.h>
+
+int main(void)
+{
+	int rv = cpuidle_state_count(0);
+	return rv;
+}