cross_tools: allow specifying a custom sysroot path

* Use with --sysroot /path/to/sysroot; useful for CI
  environments and cross-building.

Change-Id: I27a93a5d209cd5324591587e85fce9b47c18172d
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5318
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

build/scripts/build_cross_tools_gcc4

@@ -161,7 +161,7 @@ binutilsObjDir="$objDir/binutils"
 gccObjDir="$objDir/gcc"
 gdbObjDir="$objDir/gdb"
 stdcxxObjDir="$objDir/stdcxx"
-sysrootDir="$installDir/sysroot"
+sysrootDir=${HAIKU_USE_SYSROOT:-"$installDir/sysroot"}
 tmpIncludeDir="$sysrootDir/boot/system/develop/headers"
 tmpLibDir="$sysrootDir/boot/system/develop/lib"
 
@@ -279,7 +279,11 @@ mv "$installDir/$haikuMachine/lib/libstdc++.a" \
 	"$installDir/$haikuMachine/lib/libstdc++-static.a"
 
 # remove the sysroot dir
-rm -rf "$sysrootDir"
+if [ -n "$HAIKU_USE_SYSROOT" ]; then
+	rm -rf "$sysrootDir"/boot/system/*
+else
+	rm -rf "$sysrootDir"
+fi
 
 # remove the objects dir
 rm -rf "$objDir"

configure

@@ -67,6 +67,9 @@ options:
                               on to the make building the build tools.
   --no-downloads              Do not download anything. Useful when trying to
                               bootstrap and build Haiku from source only.
+  --sysroot                   The location of the cross-compiler sysroot,
+                              primarily for CI environments or cross-compilers
+                              used outside of the Haiku build system.
   --target-arch <arch>        Haiku only: Specify the target architecture to
                               build for. Must be one of the architectures of the
                               host system. The installed build tools for that
@@ -688,6 +691,11 @@ supportedTargetArchs="
 #
 while [ $# -gt 0 ] ; do
 	case "$1" in
+		--sysroot)
+			assertparam "$1" $#
+			crossToolsSysroot=$2
+			shift 2
+			;;
 		--bootstrap)
 			assertparams "$1" 3 $#
 			HOST_HAIKU_PORTER="`absolute_path $2`"
@@ -1006,6 +1014,7 @@ else
 					HAIKU_USE_GCC_GRAPHITE_$targetArch` \
 				HAIKU_USE_GCC_PIPE=$HAIKU_USE_GCC_PIPE \
 				HAIKU_USE_GDB="$gdbSources" \
+				HAIKU_USE_SYSROOT="$crossToolsSysroot" \
 				"$script" $scriptArgs "$sourceDir" "$buildCrossTools" \
 					"$crossToolsDir" $buildCrossToolsJobs || exit 1
 			else