update gitignore files

-ignore all android-build-* folders (some were missing)
-ignore downloaded gas-preprocessor perl script (android)
-ignore contrib android i686 build folder

Change-Id: I04a7274054bdb3b94ac9b10d291aa59b0dc9aa7f

.gitignore

@@ -92,7 +92,7 @@ nbproject
 .DS_Store
 
 # Android
-/build-android-arm-linux-androideabi/
+/build-android-*/
 /extras/tools/check_sed
 /extras/tools/libtool-*.tar.xz
 

contrib/.gitignore

@@ -4,3 +4,4 @@ i386*
 x86_64-*
 arm*
 aarch64*
+i686*

extras/tools/.gitignore

@@ -4,3 +4,4 @@ build/
 */
 *.tar.gz
 *.tar.bz2
+gas-preprocessor-*.pl