https://github.com/termux/termux-packages/issues/15852

--- a/test_libucontext_posix.c
+++ b/test_libucontext_posix.c
@@ -9,6 +9,13 @@
 #include <string.h>
 #include <ucontext.h>
 
+#ifdef __ANDROID__
+int getcontext (ucontext_t *);
+int setcontext(const ucontext_t *);
+int swapcontext(ucontext_t *, const ucontext_t *);
+void makecontext(ucontext_t *, void (*)(), int, ...);
+#endif
+
 static ucontext_t ctx[3];