stage2: fix Cache deadlock and build more of TSAN

* rename is_compiler_rt_or_libc to skip_linker_dependencies
   and set it to `true` for all sub-Compilations. I believe
   this resolves the deadlock we were experiencing on Drone
   CI and on some users' computers. I will remove the CI workaround in
   a follow-up commit.
 * enabling TSAN automatically causes the Compilation to link against
   libc++ even if not requested, because TSAN depends on libc++.
 * add -fno-rtti flags where appropriate when building TSAN objects.
   Thanks Firefox317 for pointing this out.
 * TSAN support: resolve all the undefined symbols. We are still seeing
   a dependency on __gcc_personality_v0 but will resolve this one in a
   follow-up commit.
 * static libs do not try to build libc++ or libc++abi.

lib/tsan/interception/interception_linux.cpp

@@ -0,0 +1,83 @@
+//===-- interception_linux.cpp ----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is a part of AddressSanitizer, an address sanity checker.
+//
+// Linux-specific interception methods.
+//===----------------------------------------------------------------------===//
+
+#include "interception.h"
+
+#if SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD || \
+    SANITIZER_OPENBSD || SANITIZER_SOLARIS
+
+#include <dlfcn.h>   // for dlsym() and dlvsym()
+
+namespace __interception {
+
+#if SANITIZER_NETBSD
+static int StrCmp(const char *s1, const char *s2) {
+  while (true) {
+    if (*s1 != *s2)
+      return false;
+    if (*s1 == 0)
+      return true;
+    s1++;
+    s2++;
+  }
+}
+#endif
+
+static void *GetFuncAddr(const char *name, uptr wrapper_addr) {
+#if SANITIZER_NETBSD
+  // FIXME: Find a better way to handle renames
+  if (StrCmp(name, "sigaction"))
+    name = "__sigaction14";
+#endif
+  void *addr = dlsym(RTLD_NEXT, name);
+  if (!addr) {
+    // If the lookup using RTLD_NEXT failed, the sanitizer runtime library is
+    // later in the library search order than the DSO that we are trying to
+    // intercept, which means that we cannot intercept this function. We still
+    // want the address of the real definition, though, so look it up using
+    // RTLD_DEFAULT.
+    addr = dlsym(RTLD_DEFAULT, name);
+
+    // In case `name' is not loaded, dlsym ends up finding the actual wrapper.
+    // We don't want to intercept the wrapper and have it point to itself.
+    if ((uptr)addr == wrapper_addr)
+      addr = nullptr;
+  }
+  return addr;
+}
+
+bool InterceptFunction(const char *name, uptr *ptr_to_real, uptr func,
+                       uptr wrapper) {
+  void *addr = GetFuncAddr(name, wrapper);
+  *ptr_to_real = (uptr)addr;
+  return addr && (func == wrapper);
+}
+
+// Android and Solaris do not have dlvsym
+#if !SANITIZER_ANDROID && !SANITIZER_SOLARIS && !SANITIZER_OPENBSD
+static void *GetFuncAddr(const char *name, const char *ver) {
+  return dlvsym(RTLD_NEXT, name, ver);
+}
+
+bool InterceptFunction(const char *name, const char *ver, uptr *ptr_to_real,
+                       uptr func, uptr wrapper) {
+  void *addr = GetFuncAddr(name, ver);
+  *ptr_to_real = (uptr)addr;
+  return addr && (func == wrapper);
+}
+#endif  // !SANITIZER_ANDROID
+
+}  // namespace __interception
+
+#endif  // SANITIZER_LINUX || SANITIZER_FREEBSD || SANITIZER_NETBSD ||
+        // SANITIZER_OPENBSD || SANITIZER_SOLARIS