Define RCPP_NO_R_HEADERS_CHECK before all #include <Rcpp.h> usage

`#include <cpp11/R.hpp>` sets everything up the right way, and otherwise we get a warning from Rcpp which doesn't seem to end up being relevant for this use case

Author: DavisVaughan

R/register.R

@@ -89,7 +89,13 @@ cpp_register <- function(path = ".", quiet = !is_interactive(), extension = c(".
 
   extra_includes <-  character()
   if (pkg_links_to_rcpp(path)) {
-    extra_includes <- c(extra_includes, "#include <cpp11/R.hpp>", "#include <Rcpp.h>", "using namespace Rcpp;")
+    extra_includes <- c(
+      extra_includes,
+      "#include <cpp11/R.hpp>",
+      "#define RCPP_NO_R_HEADERS_CHECK",
+      "#include <Rcpp.h>",
+      "using namespace Rcpp;"
+    )
   }
 
   pkg_types <- c(

cpp11test/src/cpp11.cpp

@@ -2,6 +2,7 @@
 // clang-format off
 
 #include <cpp11/R.hpp>
+#define RCPP_NO_R_HEADERS_CHECK
 #include <Rcpp.h>
 using namespace Rcpp;
 #include "cpp11/declarations.hpp"

cpp11test/src/find-intervals.cpp

@@ -2,6 +2,7 @@
 #include "cpp11.hpp"
 using namespace cpp11;
 
+#define RCPP_NO_R_HEADERS_CHECK
 #include <Rcpp.h>
 #include <algorithm>
 using namespace Rcpp;

cpp11test/src/matrix.cpp

@@ -32,6 +32,7 @@ using namespace cpp11;
   return mat;
 }
 
+#define RCPP_NO_R_HEADERS_CHECK
 #include <Rcpp.h>
 using namespace Rcpp;
 

cpp11test/src/protect.cpp

@@ -1,7 +1,8 @@
 #include <cpp11/sexp.hpp>
 #include <vector>
 
-#include "Rcpp.h"
+#define RCPP_NO_R_HEADERS_CHECK
+#include <Rcpp.h>
 
 [[cpp11::register]] void protect_one_(SEXP x, int n) {
   for (R_xlen_t i = 0; i < n; ++i) {

cpp11test/src/release.cpp

@@ -1,7 +1,8 @@
 #include <vector>
 #include "cpp11/sexp.hpp"
 
-#include "Rcpp.h"
+#define RCPP_NO_R_HEADERS_CHECK
+#include <Rcpp.h>
 
 [[cpp11::register]] void cpp11_release_(int n) {
   std::vector<cpp11::sexp> x;

cpp11test/src/test-as.cpp

@@ -7,7 +7,8 @@
 
 #include <testthat.h>
 
-#include "Rcpp.h"
+#define RCPP_NO_R_HEADERS_CHECK
+#include <Rcpp.h>
 
 context("as_cpp-C++") {
   test_that("as_cpp<integer>(INTSEXP)") {