[Sanitizers] Avoid overload ambiguity for interceptors (llvm#100986)

Since glibc 2.40 some functions like openat make use of overloads when
built with `-D_FORTIFY_SOURCE=2`, see:
https://github.com/bminor/glibc/blob/master/io/bits/fcntl2.h

This means that doing something like `(uintptr_t) openat` or `(void *)
openat` is now ambiguous, breaking the compiler-rt build on new glibc
versions.

Fix this by explicitly casting the symbol to the expected function type
before casting it to an intptr. The expected type is obtained as
`decltype(REAL(func))` so we don't have to repeat the signature from
INTERCEPTOR in the INTERCEPT_FUNTION macro.

Fixes llvm#100754.

compiler-rt/lib/interception/interception_linux.h

@@ -28,20 +28,22 @@ bool InterceptFunction(const char *name, const char *ver, uptr *ptr_to_real,
                        uptr func, uptr trampoline);
 }  // namespace __interception
 
-#define INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func) \
-  ::__interception::InterceptFunction(            \
-      #func,                                      \
-      (::__interception::uptr *)&REAL(func),      \
-      (::__interception::uptr)&(func),            \
-      (::__interception::uptr)&TRAMPOLINE(func))
+// Cast func to type of REAL(func) before casting to uptr in case it is an
+// overloaded function, which is the case for some glibc functions when
+// _FORTIFY_SOURCE is used. This disambiguates which overload to use.
+#define INTERCEPT_FUNCTION_LINUX_OR_FREEBSD(func)            \
+  ::__interception::InterceptFunction(                       \
+      #func, (::__interception::uptr *)&REAL(func),          \
+      (::__interception::uptr)(decltype(REAL(func)))&(func), \
+      (::__interception::uptr) &TRAMPOLINE(func))
 
 // dlvsym is a GNU extension supported by some other platforms.
 #if SANITIZER_GLIBC || SANITIZER_FREEBSD || SANITIZER_NETBSD
 #define INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver) \
   ::__interception::InterceptFunction(                        \
       #func, symver,                                          \
       (::__interception::uptr *)&REAL(func),                  \
-      (::__interception::uptr)&(func),                        \
+      (::__interception::uptr)(decltype(REAL(func)))&(func),  \
       (::__interception::uptr)&TRAMPOLINE(func))
 #else
 #define INTERCEPT_FUNCTION_VER_LINUX_OR_FREEBSD(func, symver) \