[Darwin, testsuite, committed] Fix isysroot-1.c for Darwin versions with fixincludes for stdio.h.

[Iain Sandoe]

For the test to succeed there needs to be some header that is to be found in
the 'expected' place i.e. <sysroot>/usr/include/.  It's important that it is 
not the
name of a header for which fixincludes have been applied, since such headers
will be found in the gcc include-fixed dir and, in general, reference additional
headers.  The dummy sysroot will prevent the additional headers from being
found, resulting in a failed test.  The fix is to use a header name that isn’t
expected to be present in a real sysroot.

tested on x86_64-darwin18, x86_64-darwin16, applied to mainline
thanks
Iain

2019-06-24  Iain Sandoe  <i...@sandoe.co.uk>

        * gcc.dg/cpp/isysroot-1.c (main): Use <example.h> as the test header.
        * gcc.dg/cpp/usr/include/stdio.h: Rename...
        * gcc.dg/cpp/usr/include/example.h: ... to this.

diff --git a/gcc/testsuite/gcc.dg/cpp/isysroot-1.c 
b/gcc/testsuite/gcc.dg/cpp/isysroot-1.c
index 7263ce4..4c54f9e 100644
--- a/gcc/testsuite/gcc.dg/cpp/isysroot-1.c
+++ b/gcc/testsuite/gcc.dg/cpp/isysroot-1.c
@@ -1,10 +1,17 @@
 /* { dg-options "-isysroot ${srcdir}/gcc.dg/cpp" } */
 /* { dg-do compile  { target *-*-darwin* } } */
 
-#include <stdio.h>
+/* For the test to succeed there needs to be some header that is to be found
+   in the 'expected' place i.e. <sysroot>/usr/include/.  It's important that
+   it is not the name of a header for which fixincludes have been applied,
+   since such headers will be found in the gcc include-fixed dir and, in
+   general, reference additional headers.  The dummy sysroot will prevent the
+   additional headers from being found, resulting in a failed test.  So use
+   a header name we don't expect to see. */
+#include <example.h>
 int main()
 {
-  /* Special stdio.h supplies function foo.  */
+  /* Special example.h supplies function foo.  */
   void (*x)(void) = foo;
   return 0;
 }
diff --git a/gcc/testsuite/gcc.dg/cpp/usr/include/example.h 
b/gcc/testsuite/gcc.dg/cpp/usr/include/example.h
new file mode 100644
index 0000000..c674e89
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/cpp/usr/include/example.h
@@ -0,0 +1,4 @@
+/* Used by gcc.dg/cpp/isysroot-1.c to test isysroot.  */
+void foo()
+{
+}
diff --git a/gcc/testsuite/gcc.dg/cpp/usr/include/stdio.h 
b/gcc/testsuite/gcc.dg/cpp/usr/include/stdio.h
deleted file mode 100644
index c674e89..0000000
--- a/gcc/testsuite/gcc.dg/cpp/usr/include/stdio.h
+++ /dev/null
@@ -1,4 +0,0 @@
-/* Used by gcc.dg/cpp/isysroot-1.c to test isysroot.  */
-void foo()
-{
-}