Refactor build_linux.sh into configure.sh

This moves all the error handling and setup into configure.sh, for a
cleaner script.

build_scripts/linux/build_linux.sh

@@ -1,21 +1,7 @@
 #!/usr/bin/env bash
 set -e
-if [[ -z $QMAKE_SPEC ]]; then
+DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
-    QMAKE_SPEC='linux-g++'
+. $DIR/configure.sh
-fi
-
-if [[ -z $USE_TIDY ]]; then
-    MAKE_COMMAND='make --jobs'
-    CLANG_TIDY=
-else
-    # Bear replaces the compile database, it does not update it.
-    # If you run 'bear make' and there is nothing to compile, you
-    # will get an empty database.
-    # Clean up the artifacts and run everything together in that case.
-    MAKE_COMMAND='bear make --jobs'
-    QMAKE_SPEC='linux-clang'
-    CLANG_TIDY='../build_scripts/linux/run-clang-tidy.sh'
-fi
 
 echo $MAKE_COMMAND
 mkdir -p build

build_scripts/linux/configure.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -e
+if [[ -z $QMAKE_SPEC ]]; then
+    QMAKE_SPEC='linux-g++'
+fi
+
+if [[ -z $USE_TIDY ]]; then
+    MAKE_COMMAND='make --jobs'
+    CLANG_TIDY=
+else
+    # Bear replaces the compile database, it does not update it.
+    # If you run 'bear make' and there is nothing to compile, you
+    # will get an empty database.
+    # Clean up the artifacts and run everything together in that case.
+    MAKE_COMMAND='bear make --jobs'
+    QMAKE_SPEC='linux-clang'
+    CLANG_TIDY='../build_scripts/linux/run-clang-tidy.sh'
+fi
+