Merge branch 'remove-ndk-r9b' into 'master'

makebuildserver: remove NDK r9b to save 1.6 GB of disk space

See merge request fdroid/fdroidserver!459

diff --cc buildserver/config.buildserver.py
Simple merge

diff --cc examples/config.py
Simple merge

diff --cc fdroidserver/common.py
Simple merge

diff --cc makebuildserver
index 2fd51b18271a20f5f05803739acd0a3cd71cf8a7,1f8ad9246e1ad0987b8d2972c98d372f4986c671..20cc386c0f32886897b5c9a2690ce2b9d8d8eb21
--- 1/makebuildserver
--- 2/makebuildserver
+++ b/makebuildserver
@@@ -349,14 -349,8 +349,10 @@@ cachefiles = 
       'e7cf7d1853dfc30c1c44f571d3919eeeedef002823b66b6a988d27e919686389'),
      ('https://downloads.gradle.org/distributions/gradle-4.5-bin.zip',
       '03f2a43a314ff0fb843a85ef68078e06d181c4549c1e5fb983f289382b59b5e3'),
 +    ('https://downloads.gradle.org/distributions/gradle-4.5.1-bin.zip',
 +     '3e2ea0d8b96605b7c528768f646e0975bd9822f06df1f04a64fd279b1a17805e'),
      ('https://dl.google.com/android/ndk/android-ndk-r10e-linux-x86_64.bin',
       '102d6723f67ff1384330d12c45854315d6452d6510286f4e5891e00a5a8f1d5a'),
-     ('https://dl.google.com/android/ndk/android-ndk-r9b-linux-x86_64.tar.bz2',
-      '8956e9efeea95f49425ded8bb697013b66e162b064b0f66b5c75628f76e0f532'),
-     ('https://dl.google.com/android/ndk/android-ndk-r9b-linux-x86_64-legacy-toolchains.tar.bz2',
-      'de93a394f7c8f3436db44568648f87738a8d09801a52f459dcad3fc047e045a1'),
      ('https://dl.google.com/android/repository/android-ndk-r11c-linux-x86_64.zip',
       'ba85dbe4d370e4de567222f73a3e034d85fc3011b3cbd90697f3e8dcace3ad94'),
      ('https://dl.google.com/android/repository/android-ndk-r12b-linux-x86_64.zip',