cmake: check for alloca() in stdlib.h and malloc.h, too (bug #5316)

CMakeLists.txt

@@ -848,7 +848,12 @@ if(LIBC)
 
     if(NOT APPLE)
       check_include_file(alloca.h HAVE_ALLOCA_H)
-      check_symbol_exists(alloca "alloca.h" HAVE_ALLOCA)
+      check_symbol_exists(alloca "alloca.h" HAVE_ALLOCA1)
+      check_symbol_exists(alloca "stdlib.h" HAVE_ALLOCA2)
+      check_symbol_exists(alloca "malloc.h" HAVE_ALLOCA3)
+      if(HAVE_ALLOCA1 OR HAVE_ALLOCA2 OR HAVE_ALLOCA3)
+        set(HAVE_ALLOCA 1)
+      endif()
     else()
       set(HAVE_ALLOCA_H 1)
       set(HAVE_ALLOCA 1)