[SDKS] Fix Android SDK build on Linux (#8022)

Current build uses `tar` to extract ZIP archives. This works with BSD
tar but not with GNU tar, alas. Tar was used in order to strip the root
directory of Android archive while moving files into place. This commit
replaces `tar` with a call to a shell script (because doing what it does
using Make defines is an exercise in pain) which works both on macOS/BSD
and on Linux.

2 files changed, 36 insertions, 3 deletions

diff --git a/sdks/builds/android.mk b/sdks/builds/android.mk
index 067ac88938c..acb1f7600c3 100644
--- a/sdks/builds/android.mk
+++ b/sdks/builds/android.mk
@@ -24,8 +24,7 @@ $$(ANDROID_TOOLCHAIN_CACHE_DIR)/$(1).zip: | $$(ANDROID_TOOLCHAIN_CACHE_DIR)
 
 $$(ANDROID_TOOLCHAIN_DIR)/$(3)$$(if $(2),/$(2))/.stamp-$(1): $$(ANDROID_TOOLCHAIN_CACHE_DIR)/$(1).zip
 	rm -rf $$(ANDROID_TOOLCHAIN_DIR)/$(3)$$(if $(2),/$(2))
-	mkdir -p $$(ANDROID_TOOLCHAIN_DIR)/$(3)$$(if $(2),/$(2))
-	tar -xf $$< -C $$(ANDROID_TOOLCHAIN_DIR)/$(3)$$(if $(2),/$(2)) --strip-components 1
+	./unzip-android-archive.sh "$$<" "$$(ANDROID_TOOLCHAIN_DIR)/$(3)$$(if $(2),/$(2))"
 	touch $$@
 
 .PHONY: provision-android-$(3)-$(1)
@@ -58,7 +57,7 @@ $(eval $(call AndroidSDKProvisioningTemplate,emulator-darwin-4266726,emulator))
 else
 ifeq ($(UNAME),Linux)
 $(eval $(call AndroidSDKProvisioningTemplate,build-tools_r$(ANDROID_BUILD_TOOLS_VERSION)-linux,build-tools/$(ANDROID_BUILD_TOOLS_VERSION)))
-$(eval $(call AndroidSDKProvisioningTemplate,platform-tools_r27.0.1-linux,platforms-tools))
+$(eval $(call AndroidSDKProvisioningTemplate,platform-tools_r27.0.1-linux,platform-tools))
 $(eval $(call AndroidSDKProvisioningTemplate,sdk-tools-linux-4333796,tools))
 $(eval $(call AndroidSDKProvisioningTemplate,emulator-linux-4266726,emulator))
 else
diff --git a/sdks/builds/unzip-android-archive.sh b/sdks/builds/unzip-android-archive.sh
new file mode 100755
index 00000000000..01b681d684a
--- /dev/null
+++ b/sdks/builds/unzip-android-archive.sh
@@ -0,0 +1,34 @@
+#!/usr/bin/env bash
+
+set -e
+
+function cleanup()
+{
+	if [ -n "$ARCHIVE_TEMP_DIR" ]; then
+		rm -rf "$ARCHIVE_TEMP_DIR"
+	fi
+}
+
+trap cleanup 0
+
+## Parameters:
+#    $1: path to source archive
+#    $2: destination directory
+
+# This weird syntax is necessary because some zip archives do not contain a separate
+# entry for the root directory but merely a collection of its subdirectories (for instance
+# platform-tools). The very first entry in the archive is retrieved, then its path is read and
+# finally the part up to the first '/' of the path is retrieved as the root directory of
+# the archive. With platform-tools the last part is necessary because otherwise the root directory
+# would end up being reported as `platform-tools/adb` as this is the first entry in the archive and
+# there's no `platform-tools/` entry
+ZIP_ROOT_DIR=$(unzip -qql "$1" | head -n1 | tr -s ' ' | cut -d' ' -f5- | tr '/' ' ' | cut -d' ' -f1)
+
+# We need a temporary directory because some archives (emulator) have their root directory named the
+# same as a file/directory inside it (emulator has emulator/emulator executable for instance) and
+# moving such a file/directory to .. wouldn't work
+ARCHIVE_TEMP_DIR=$(mktemp -d)
+
+unzip "$1" -d "$ARCHIVE_TEMP_DIR"
+mkdir -p "$2"
+find "$ARCHIVE_TEMP_DIR/$ZIP_ROOT_DIR/" -maxdepth 1 -not \( -name "$ZIP_ROOT_DIR" -and -type d \) -and -not -name . -and -not -name .. -exec mv -f '{}' "$2" ';'