build fail on Debian Jessie (cmake too old)

[metux]

error: failed to run custom build command for gecko-media v0.1.0 (https://github.com/servo/gecko-media.git#fe437442)
process didn't exit successfully: /home/nekrad/src/moz/servo/target/release/build/gecko-media-d88f39a9af0ed77e/build-script-build (exit code: 101)
--- stdout
running: "cmake" "/home/nekrad/src/moz/servo/.cargo/git/checkouts/gecko-media-6bedb392a81eb7cf/fe43744/gecko-media/." "-DCMAKE_INSTALL_PREFIX=/home/nekrad/src/moz/servo/target/release/build/gecko-media-b339222d8f24477b/out" "-DCMAKE_C_FLAGS= -ffunction-sections -fdata-sections -fPIC -m64" "-DCMAKE_C_COMPILER=/usr/bin/cc" "-DCMAKE_CXX_FLAGS= -ffunction-sections -fdata-sections -fPIC -m64" "-DCMAKE_CXX_COMPILER=/usr/bin/c++" "-DCMAKE_BUILD_TYPE=Release"
-- The C compiler identification is GNU 4.9.2
-- The CXX compiler identification is GNU 4.9.2
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Configuring incomplete, errors occurred!
See also "/home/nekrad/src/moz/servo/target/release/build/gecko-media-b339222d8f24477b/out/build/CMakeFiles/CMakeOutput.log".

--- stderr
CMake Error at CMakeLists.txt:335 (target_sources):
Unknown CMake command "target_sources".

Jessie has cmake 3.0.2 - target_sources" had been introduced w/ cmake 3.1.

[metux]

A workaround is taking cmake from jessie-backports.
There should be some information printed out about that - see #19624

[fabricedesre]

Looks like https://github.com/servo/gecko-media/blob/master/gecko-media/CMakeLists.txt#L1 should be updated to 3.1