Merge #7487: Workaround Travis-side CI issues

149641e Travis: Use Blue Box VMs for IPv6 loopback support (Luke Dashjr)
c01f08d Bugfix: depends/Travis: Use --location (follow redirects) and --fail [on HTTP error response] with curl (Luke Dashjr)
5d1148c Travis: Use curl rather than wget for Mac SDK (Luke Dashjr)
1ecbb3b depends: Use curl for fetching on Linux (Luke Dashjr)

.travis.yml

@@ -3,6 +3,12 @@
 #   compiler key (which we don't use anyway). This is worked around for now by
 #   replacing the "compilers" with a build name prefixed by the no-op ":"
 #   command. See: https://github.com/travis-ci/travis-ci/issues/4393
+# - sudo/dist/group are set so as to get Blue Box VMs, necessary for [loopback]
+#   IPv6 support
+
+sudo: required
+dist: precise
+group: legacy
 
 os: linux
 language: cpp
@@ -52,7 +58,7 @@ install:
 before_script:
     - unset CC; unset CXX
     - mkdir -p depends/SDKs depends/sdk-sources
-    - if [ -n "$OSX_SDK" -a ! -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then wget $SDK_URL/MacOSX${OSX_SDK}.sdk.tar.gz -O depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz; fi
+    - if [ -n "$OSX_SDK" -a ! -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then curl --location --fail $SDK_URL/MacOSX${OSX_SDK}.sdk.tar.gz -o depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz; fi
     - if [ -n "$OSX_SDK" -a -f depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz ]; then tar -C depends/SDKs -xf depends/sdk-sources/MacOSX${OSX_SDK}.sdk.tar.gz; fi
     - make $MAKEJOBS -C depends HOST=$HOST $DEP_OPTS
 script:

depends/builders/darwin.mk

@@ -7,7 +7,7 @@ build_darwin_OTOOL: = $(shell xcrun -f otool)
 build_darwin_NM: = $(shell xcrun -f nm)
 build_darwin_INSTALL_NAME_TOOL:=$(shell xcrun -f install_name_tool)
 build_darwin_SHA256SUM = shasum -a 256
-build_darwin_DOWNLOAD = curl --connect-timeout $(DOWNLOAD_CONNECT_TIMEOUT) --retry $(DOWNLOAD_RETRIES) -L -o
+build_darwin_DOWNLOAD = curl --location --fail --connect-timeout $(DOWNLOAD_CONNECT_TIMEOUT) --retry $(DOWNLOAD_RETRIES) -L -o
 
 #darwin host on darwin builder. overrides darwin host preferences.
 darwin_CC=$(shell xcrun -f clang) -mmacosx-version-min=$(OSX_MIN_VERSION)

depends/builders/linux.mk

@@ -1,2 +1,2 @@
 build_linux_SHA256SUM = sha256sum
-build_linux_DOWNLOAD = wget --timeout=$(DOWNLOAD_CONNECT_TIMEOUT) --tries=$(DOWNLOAD_RETRIES) -nv -O
+build_linux_DOWNLOAD = curl --location --fail --connect-timeout $(DOWNLOAD_CONNECT_TIMEOUT) --retry $(DOWNLOAD_RETRIES) -L -o