From 4746def4a207eb6eea58e8f39d434f46340cc293 Mon Sep 17 00:00:00 2001
From: David Michael <fedora.dm0@gmail.com>
Date: Sat, 23 Feb 2019 10:36:23 -0500
Subject: [PATCH] Implement a pseudo-toolset for cross-compiling (#196)

When running build.sh with the cross-cc toolset, it uses the native
compiler settings found in the BUILD_CC, BUILD_CFLAGS, and
BUILD_LDFLAGS environment variables to create executables to run on
the build system.  It then sets the toolset to cc so that the
cross-compilers given as CC etc. are propagated to subprocesses.
This ensures both that the build system can build and execute its
required programs and that final executables are cross-compiled for
the target architecture.
---
 src/engine/build.sh | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/src/engine/build.sh b/src/engine/build.sh
index 7e46e387e..005e4d9ba 100755
--- a/src/engine/build.sh
+++ b/src/engine/build.sh
@@ -40,6 +40,12 @@ error_exit ()
     echo "### detected. The 'cc' toolset will use the CC, CFLAGS, and LIBS"
     echo "### environment variables, if present."
     echo "###"
+    echo "### Similarly, the cross-cc toolset is available for cross-compiling"
+    echo "### by using the BUILD_CC, BUILD_CFLAGS, and BUILD_LDFLAGS environment"
+    echo "### variables to compile binaries that will be executed on the build"
+    echo "### system. This allows CC etc. to be set for cross-compilers to be"
+    echo "### propagated to subprocesses."
+    echo "###"
     exit 1
 }
 
@@ -268,6 +274,15 @@ case $BOOST_JAM_TOOLSET in
     BOOST_JAM_OPT_YYACC="$BOOST_JAM_OPT_YYACC $CFLAGS $LIBS"
     ;;
 
+    cross-cc)
+    if test -z "$BUILD_CC" ; then BUILD_CC=cc ; fi
+    BOOST_JAM_CC=$BUILD_CC
+    BOOST_JAM_OPT_JAM="$BOOST_JAM_OPT_JAM $BUILD_CFLAGS $BUILD_LDFLAGS"
+    BOOST_JAM_OPT_MKJAMBASE="$BOOST_JAM_OPT_MKJAMBASE $BUILD_CFLAGS $BUILD_LDFLAGS"
+    BOOST_JAM_OPT_YYACC="$BOOST_JAM_OPT_YYACC $BUILD_CFLAGS $BUILD_LDFLAGS"
+    BOOST_JAM_TOOLSET=cc
+    ;;
+
     qcc)
     BOOST_JAM_CC=qcc
     ;;