Update toolchain to support OS X down to 10.6 (#275)

Author: igrr

build/build_board_manager_package.sh

@@ -81,10 +81,10 @@ cat << EOF > package_esp8266com_index.json
         },
         {
             "host":"x86_64-apple-darwin",
-            "url":"https://github.com/igrr/esptool-ck/releases/download/0.4.4/esptool-0.4.4-osx.tar.gz",
-            "archiveFileName":"esptool-0.4.4-osx.tar.gz",
-            "checksum":"SHA-256:bb2a58c3583f9dcb0d3e7611531a0f3a29c21a4a1c442987bb29d07408824dfe",
-            "size":"12145"
+            "url":"https://download.esp8266.com/esptool-0.4.4-5-g744c44d-osx.tar.gz",
+            "archiveFileName":"esptool-0.4.4-5-g744c44d-osx.tar.gz",
+            "checksum":"SHA-256:d8bc920e046fcc668b31cda63ac5553b4c07a6db12bfd0abc9005fc94628afcb",
+            "size":"12133"
         },
         {
             "host":"x86_64-pc-linux-gnu",
@@ -115,10 +115,10 @@ cat << EOF > package_esp8266com_index.json
         },
         {
            "host":"x86_64-apple-darwin",
-           "url":"http://arduino.esp8266.com/osx-xtensa-lx106-elf-gb404fb9.tar.gz",
-           "archiveFileName":"osx-xtensa-lx106-elf-gb404fb9.tar.gz",
-           "checksum":"SHA-256:540be2ca32637584463a4a4d04717f6c79c7355e336b8c3578b0947218cf92b9",
-           "size":"35189446"
+           "url":"http://arduino.esp8266.com/osx-xtensa-lx106-elf-gb404fb9-2.tar.gz",
+           "archiveFileName":"osx-xtensa-lx106-elf-gb404fb9-2.tar.gz",
+           "checksum":"SHA-256:0cf150193997bd1355e0f49d3d49711730035257bc1aee1eaaad619e56b9e4e6",
+           "size":"35385382"
         },
         {
            "host":"x86_64-pc-linux-gnu",