common.mak: Introduce user-defined function check_header_prereq()

The new user-defined function allows to check for C headers in
make's conditional statements.

Example:

ifeq ($(call check_header_prereq,"systemd/sd-daemon.h"),yes)
  $(warning "systemd support enabled")
else
  $(warning "systemd support disabled")
endif

Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
Acked-by: Jan Höppner <hoeppner@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

common.mak

@@ -111,6 +111,20 @@ ifeq ("${ASAN}","1")
 	DEFAULT_LDFLAGS += -fsanitize=address
 endif
 
+#
+# Check for header prerequisite
+#
+# $1: Name of include file to check
+# $2: Additional compiler & linker options (optional)
+#
+# Returns "yes" on success and nothing otherwise
+#
+define check_header_prereq
+$(shell printf "#include <%s>\n int main(void) {return 0;}" $1 | \
+        ( $(CC) $(filter-out --coverage, $(ALL_CFLAGS)) $(ALL_CPPFLAGS) \
+                $2 -o /dev/null -xc - ) >/dev/null 2>&1 && echo -n yes)
+endef
+
 #
 # Check for build dependency
 #