From 26c2f23f36228e334d17c43a0cb61f76cc545c3d Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Thu, 10 Mar 2022 12:35:39 +0100
Subject: build: Fix Boost.Process detection on macOS arm64

Could be tested as follows:
```
% brew install boost@1.76
% ./autogen.sh
% ./configure --with-boost='/opt/homebrew/opt/boost@1.76'
```

Github-Pull: bitcoin#24521
Rebased-From: 1d4157a
---
 configure.ac | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/configure.ac b/configure.ac
index 36094e7b32..8debf98379 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1438,6 +1438,8 @@ if test "$use_external_signer" != "no"; then
     ;;
     *)
       AC_MSG_CHECKING([whether Boost.Process can be used])
+      TEMP_CPPFLAGS="$CPPFLAGS"
+      CPPFLAGS="$CPPFLAGS $BOOST_CPPFLAGS"
       TEMP_LDFLAGS="$LDFLAGS"
       dnl Boost 1.73 and older require the following workaround.
       LDFLAGS="$LDFLAGS $PTHREAD_CFLAGS"
@@ -1445,6 +1447,7 @@ if test "$use_external_signer" != "no"; then
         [have_boost_process="yes"],
         [have_boost_process="no"])
       LDFLAGS="$TEMP_LDFLAGS"
+      CPPFLAGS="$TEMP_CPPFLAGS"
       AC_MSG_RESULT([$have_boost_process])
       if test "$have_boost_process" = "yes"; then
         use_external_signer="yes"
-- 
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