Fix more usages of LLVM version

Change-Id: I73985c52be2837496590443f7c990466712ec037

c_glib/Brewfile

@@ -24,7 +24,7 @@ brew "git"
 brew "gobject-introspection"
 brew "gtk-doc"
 brew "libtool"
-brew "llvm@6"
+brew "llvm@7"
 brew "lua"
 brew "luarocks"
 brew "ninja"

ci/travis_env_common.sh

@@ -26,6 +26,9 @@ export CONDA_BINUTILS_VERSION=2.31
 export ARROW_LLVM_VERSION=7.0
 export CONDA_LLVM_VERSION="7.0.*"
 
+# extract the major version
+export ARROW_LLVM_MAJOR_VERSION=$(echo $ARROW_LLVM_VERSION | cut -d. -f1)
+
 export ARROW_CPP_DIR=$TRAVIS_BUILD_DIR/cpp
 export ARROW_PYTHON_DIR=$TRAVIS_BUILD_DIR/python
 export ARROW_C_GLIB_DIR=$TRAVIS_BUILD_DIR/c_glib

ci/travis_install_linux.sh

@@ -39,7 +39,7 @@ fi
 
 set -x
 if [ "$ARROW_TRAVIS_GANDIVA" == "1" ]; then
-    sudo apt-get install -y -qq llvm-$ARROW_LLVM_VERSION-dev
+    sudo apt-get install -y -qq llvm-$ARROW_LLVM_MAJOR_VERSION-dev
 fi
 
 set -x

r/lint.sh

@@ -20,8 +20,7 @@
 SOURCE_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
 CPP_BUILD_SUPPORT=$SOURCE_DIR/../cpp/build-support
 
-LLVM_VERSION=6.0
-CLANG_FORMAT=clang-format-$LLVM_VERSION
+CLANG_FORMAT=clang-format-7
 
 $CPP_BUILD_SUPPORT/run_clang_format.py \
     --clang_format_binary=$CLANG_FORMAT \