package/libcurl: fix build when !BR2_TOOLCHAIN_HAS_SYNC_1

On platform that do not provide __atomic_exchange_1(), and when
libatomic is not available (e.g., threads support disabled) link of
libcurl.so fails. To solve this use an indirect way to make HAVE_ATOMIC
undefined. Add an upstream patch for checking the stdatomic.h header,
and seed the 'no' answer.

Fixes:
http://autobuild.buildroot.net/results/8f695d4dbb91cfde8e93ab38e837b0a0042b986b/
http://autobuild.buildroot.net/results/3b4712b0ace52da1650e88cdaafb6a20be135464/

Cc: Matt Weber <matthew.weber@collins.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

package/libcurl/0002-configure-check-for-the-stdatomic.h-header-in-config.patch

@@ -0,0 +1,70 @@
+From a68074b5db2a1fb637853b808e5b263c2ce9cbdd Mon Sep 17 00:00:00 2001
+From: Daniel Stenberg <daniel@haxx.se>
+Date: Tue, 28 Jun 2022 08:37:22 +0200
+Subject: [PATCH] configure: check for the stdatomic.h header in configure
+
+... and only set HAVE_ATOMIC if that header exists since we use
+typedefes set in it.
+
+Reported-by: Ryan Schmidt
+Fixes #9059
+Closes #9060
+
+Signed-off-by: Baruch Siach <baruch@tkos.co.il>
+---
+Upstream status: commit a68074b5db2a1fb637853b808e5b263c2ce9cbdd
+
+ m4/curl-functions.m4 | 36 +++++++++++++++++++-----------------
+ 1 file changed, 19 insertions(+), 17 deletions(-)
+
+diff --git a/m4/curl-functions.m4 b/m4/curl-functions.m4
+index ec406f56aed8..f3e12a53a9fd 100644
+--- a/m4/curl-functions.m4
++++ b/m4/curl-functions.m4
+@@ -6570,24 +6570,26 @@ AC_DEFUN([CURL_COVERAGE],[
+ ])
+ 
+ dnl CURL_ATOMIC
+-dnl --------------------------------------------------
+-dnl Check if _Atomic works
++dnl -------------------------------------------------------------
++dnl Check if _Atomic works. But only check if stdatomic.h exists.
+ dnl
+ AC_DEFUN([CURL_ATOMIC],[
+-  AC_MSG_CHECKING([if _Atomic is available])
+-  AC_COMPILE_IFELSE([
+-    AC_LANG_PROGRAM([[
+-      $curl_includes_unistd
+-    ]],[[
+-      _Atomic int i = 0;
+-    ]])
+-  ],[
+-    AC_MSG_RESULT([yes])
+-    AC_DEFINE_UNQUOTED(HAVE_ATOMIC, 1,
+-      [Define to 1 if you have _Atomic support.])
+-    tst_atomic="yes"
+-  ],[
+-    AC_MSG_RESULT([no])
+-    tst_atomic="no"
++  AC_CHECK_HEADERS(stdatomic.h, [
++    AC_MSG_CHECKING([if _Atomic is available])
++    AC_COMPILE_IFELSE([
++      AC_LANG_PROGRAM([[
++        $curl_includes_unistd
++      ]],[[
++        _Atomic int i = 0;
++      ]])
++    ],[
++      AC_MSG_RESULT([yes])
++      AC_DEFINE_UNQUOTED(HAVE_ATOMIC, 1,
++        [Define to 1 if you have _Atomic support.])
++      tst_atomic="yes"
++    ],[
++      AC_MSG_RESULT([no])
++      tst_atomic="no"
++    ])
+   ])
+ ])
+-- 
+2.35.1
+

package/libcurl/libcurl.mk

@@ -15,6 +15,8 @@ LIBCURL_LICENSE_FILES = COPYING
 LIBCURL_CPE_ID_VENDOR = haxx
 LIBCURL_CPE_ID_PRODUCT = libcurl
 LIBCURL_INSTALL_STAGING = YES
+# We are patching configure.ac
+LIBCURL_AUTORECONF = YES
 
 # We disable NTLM support because it uses fork(), which doesn't work
 # on non-MMU platforms. Moreover, this authentication method is
@@ -36,6 +38,12 @@ ifeq ($(BR2_TOOLCHAIN_HAS_LIBATOMIC),y)
 LIBCURL_CONF_OPTS += LIBS=-latomic
 endif
 
+ifeq ($(BR2_TOOLCHAIN_HAS_SYNC_1),)
+# Even though stdatomic.h does exist, link fails for __atomic_exchange_1
+# Work around this by pretending atomics aren't available.
+LIBCURL_CONF_ENV += ac_cv_header_stdatomic_h=no
+endif
+
 ifeq ($(BR2_PACKAGE_LIBCURL_VERBOSE),y)
 LIBCURL_CONF_OPTS += --enable-verbose
 else