[clang-scan-deps] use `-Wno-error` when scanning for dependencies

[arphaman]

Summary

Warning can be promoted to errors. But that shouldn't prevent us from getting the dependencies!

[Bigcheese]

LGTM

[dexonsmith]

Is warning output suppressed? If so, should we just/also disable all warnings? (IIRC, the flag is -w.)

cfe/trunk/test/ClangScanDeps/Inputs/no-werror.json

+[
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/no-werror.cpp -IInputs -std=c++17 -Weverything -Werror",
+  "file": "DIR/no-werror.cpp"
+}
+]

cfe/trunk/test/ClangScanDeps/Inputs/sys-header.h

+#define MACRO 201411

cfe/trunk/test/ClangScanDeps/no-werror.cpp

+// RUN: rm -rf %t.dir
+// RUN: rm -rf %t.cdb
+// RUN: mkdir -p %t.dir
+// RUN: cp %s %t.dir/no-werror.cpp
+// RUN: mkdir %t.dir/Inputs
+// RUN: cp %S/Inputs/sys-header.h %t.dir/Inputs/sys-header.h
+// RUN: sed -e "s|DIR|%/t.dir|g" %S/Inputs/no-werror.json > %t.cdb
+//
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 1 | FileCheck %s
+
+#define MACRO 201411L
+
+#include "sys-header.h"
+
+// CHECK: no-werror.cpp
+// CHECK-NEXT: Inputs{{/|\\}}sys-header.h

cfe/trunk/tools/clang-scan-deps/ClangScanDeps.cpp

AdjustingCompilations->appendArgumentsAdjuster(
       [](const tooling::CommandLineArguments &Args, StringRef /*unused*/) {
         tooling::CommandLineArguments AdjustedArgs = Args;
         AdjustedArgs.push_back("-o");
         AdjustedArgs.push_back("/dev/null");
         AdjustedArgs.push_back("-Xclang");
         AdjustedArgs.push_back("-Eonly");
         AdjustedArgs.push_back("-Xclang");
         AdjustedArgs.push_back("-sys-header-deps");
+        AdjustedArgs.push_back("-Wno-error");
         return AdjustedArgs;
       });
 
   SharedStream Errs(llvm::errs());
   // Print out the dependency results to STDOUT by default.
   SharedStream DependencyOS(llvm::outs());
   unsigned NumWorkers =
       NumThreads == 0 ? llvm::hardware_concurrency() : NumThreads;