perf tools: Add an option to build without libbfd

Some distributions, like debian, don't link perf with libbfd. Add a
build flag to make this configuration buildable and testable.

This was inspired by:

https://lore.kernel.org/linux-perf-users/[e-mail]/T/#u

Signed-off-by: Ian Rogers <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: tony garnock-jones <[e-mail]>
Link: http://lore.kernel.org/lkml/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/Makefile.config

···
   endif
 endif
 
-ifeq ($(feature-libbfd), 1)
-  EXTLIBS += -lbfd -lopcodes
-else
-  # we are on a system that requires -liberty and (maybe) -lz
-  # to link against -lbfd; test each case individually here
 
-  # call all detections now so we get correct
-  # status in VF output
-  $(call feature_check,libbfd-liberty)
-  $(call feature_check,libbfd-liberty-z)
-
-  ifeq ($(feature-libbfd-liberty), 1)
-    EXTLIBS += -lbfd -lopcodes -liberty
-    FEATURE_CHECK_LDFLAGS-disassembler-four-args += -liberty -ldl
+ifndef NO_LIBBFD
+  ifeq ($(feature-libbfd), 1)
+    EXTLIBS += -lbfd -lopcodes
   else
-    ifeq ($(feature-libbfd-liberty-z), 1)
-      EXTLIBS += -lbfd -lopcodes -liberty -lz
-      FEATURE_CHECK_LDFLAGS-disassembler-four-args += -liberty -lz -ldl
-    endif
-  endif
-  $(call feature_check,disassembler-four-args)
-endif
+    # we are on a system that requires -liberty and (maybe) -lz
+    # to link against -lbfd; test each case individually here
 
-ifeq ($(feature-libbfd-buildid), 1)
-  CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
-else
-  msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
+    # call all detections now so we get correct
+    # status in VF output
+    $(call feature_check,libbfd-liberty)
+    $(call feature_check,libbfd-liberty-z)
+
+    ifeq ($(feature-libbfd-liberty), 1)
+      EXTLIBS += -lbfd -lopcodes -liberty
+      FEATURE_CHECK_LDFLAGS-disassembler-four-args += -liberty -ldl
+    else
+      ifeq ($(feature-libbfd-liberty-z), 1)
+        EXTLIBS += -lbfd -lopcodes -liberty -lz
+        FEATURE_CHECK_LDFLAGS-disassembler-four-args += -liberty -lz -ldl
+      endif
+    endif
+    $(call feature_check,disassembler-four-args)
+  endif
+
+  ifeq ($(feature-libbfd-buildid), 1)
+    CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
+  else
+    msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
+  endif
 endif
 
 ifdef NO_DEMANGLE