[newlib-cygwin] libgloss: build with -nostdinc

[Michael Frysinger]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=e0c0ad8268af60a2413edcab84320eef1e6ce5f9

commit e0c0ad8268af60a2413edcab84320eef1e6ce5f9
Author: Mike Frysinger <vapier@gentoo.org>
Date:   Sat Feb 12 01:59:13 2022 -0500

    libgloss: build with -nostdinc
    
    We don't want libgloss building against C library headers that happened
    to be installed with the toolchain, so add -nostdinc to the build.  We
    still need access to the compiler internal headers, so probe those and
    include them via -isystem.  This uses a similar probing style as glibc,
    which has used it for over a decade, so it should be safe & stable.
    
    This should prevent any latent bugs due to testing with a toolchain that
    is fully configured & installed already.

Diff:
---
 libgloss/configure    | 20 ++++++++++++++++++++
 libgloss/configure.ac | 11 +++++++++++
 2 files changed, 31 insertions(+)

diff --git a/libgloss/configure b/libgloss/configure
index abe3a574c..215a5c7a5 100755
--- a/libgloss/configure
+++ b/libgloss/configure
@@ -5104,6 +5104,26 @@ esac
 
 
 
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for compiler search settings" >&5
+$as_echo_n "checking for compiler search settings... " >&6; }
+if ${libc_cv_compiler_isystem+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+    for subdir in include include-fixed; do
+    if dir=`$CC -print-file-name=$subdir`; then :
+        if test -n "$dir"; then :
+          libc_cv_compiler_isystem="$libc_cv_compiler_isystem -isystem $dir"
+
+fi
+
+fi
+  done
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $libc_cv_compiler_isystem" >&5
+$as_echo "$libc_cv_compiler_isystem" >&6; }
+CC="$CC -nostdinc $libc_cv_compiler_isystem"
+
 host_makefile_frag_path=$host_makefile_frag
 
 
diff --git a/libgloss/configure.ac b/libgloss/configure.ac
index 78e92a0e8..06d17d8b5 100644
--- a/libgloss/configure.ac
+++ b/libgloss/configure.ac
@@ -336,6 +336,17 @@ m4_include([mcore/acinclude.m4])
 m4_include([mn10300/acinclude.m4])
 m4_include([moxie/acinclude.m4])
 
+AC_CACHE_CHECK([for compiler search settings], libc_cv_compiler_isystem, [dnl
+  for subdir in include include-fixed; do
+    AS_IF([dir=`$CC -print-file-name=$subdir`], [dnl
+      AS_IF([test -n "$dir"], [dnl
+        libc_cv_compiler_isystem="$libc_cv_compiler_isystem -isystem $dir"
+      ])
+    ])
+  done
+])
+CC="$CC -nostdinc $libc_cv_compiler_isystem"
+
 dnl We have to assign the same value to other variables because autoconf
 dnl doesn't provide a mechanism to substitute a replacement keyword with
 dnl arbitrary data or pathnames.