From effd0dbae8bd7b21d386cb68653e80a87e82e6bf Mon Sep 17 00:00:00 2001
From: Ryan Gardner <ryan.gardner@coxautoinc.com>
Date: Mon, 17 May 2021 19:43:51 -0400
Subject: [PATCH] Make the Mac SDK detection in build.sh more robust

When trying to build on Big Sur, the xcode command-line tools
install are installed in /Library/Developer/CommandLineTools/SDKs,
and as of Xcode 12.5, it does not include a 10.x version
of SDK.

This changes it to search in the location of the command-line tools SDK
for a 10.x version, and if it can't find a 10.x version it will
find an explicit 11.x version of the SDK to use because it is
conceivable that in the near future Apple will stop installing any
10.x SDK's as part of the command-line tool installer.

If the SDK can't be found, the build script will exit now instead
of continuing with an unset BASESDK version that causes a later failure.

Signed-off-by: Ryan Gardner <ryan.gardner@coxautoinc.com>
---
 scripts/build.sh | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/scripts/build.sh b/scripts/build.sh
index 52e30c0c9..133c483f2 100755
--- a/scripts/build.sh
+++ b/scripts/build.sh
@@ -147,6 +147,8 @@ fi
 if [ "$PLATFORM" = Darwin ] ; then
 	if [ -d /Developer/SDKs ] ; then
 		SDKROOT=/Developer/SDKs
+	elif [ -d  /Library/Developer/CommandLineTools/SDKs ] ; then
+		SDKROOT=/Library/Developer/CommandLineTools/SDKs
 	elif [ -d /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs ] ; then
 		SDKROOT=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs
 	else
@@ -154,10 +156,20 @@ if [ "$PLATFORM" = Darwin ] ; then
 		echo "/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs)"
 		exit 1;
 	fi
+	# find a 10.x base SDK to use, or if none can be found, find a numbered 11.x base SDK to use
 	BASESDK=$(ls $SDKROOT | grep "MacOSX10\.1.\.sdk" | head -1 | sed -e "s/MacOSX//;s/\.sdk//")
-	OLDER_MAC="-mmacosx-version-min=10.11 -isysroot${SDKROOT}/MacOSX${BASESDK}.sdk"
+	if [ -z "$BASESDK" ] ; then
+	  BASESDK=$(ls $SDKROOT | grep -E "MacOSX11\.[0-9]+\.sdk" | head -1 | sed -e "s/MacOSX//;s/\.sdk//")
+	  if [ -z "$BASESDK" ] ; then
+	    echo "Cannot find a base SDK of type 10.x or 11.x under the SDK root of ${SDKROOT}"
+	    exit 1;
+    fi
+  fi
+  echo "Using ${BASESDK} as the BASESDK under ${SDKROOT}"
+
+	OLDER_MAC="-mmacosx-version-min=${BASESDK} -isysroot${SDKROOT}/MacOSX${BASESDK}.sdk"
 	OLDER_MAC_CMAKE="-DCMAKE_OSX_DEPLOYMENT_TARGET=${BASESDK} -DCMAKE_OSX_SYSROOT=${SDKROOT}/MacOSX${BASESDK}.sdk/"
-	if [[ ! -d /usr/include && ! -d "${SDKROOT}/MacOSX.sdk/usr/include" ]] ; then
+	if [[ ! -d /usr/include && ! -d "${SDKROOT}/MacOSX${BASESDK}.sdk/usr/include" ]] ; then
 		echo "Error: Xcode Command Line Tools are not installed"
 		echo ""
 		echo "Please run:"