Temporarily disable LLVM assertions on Travis

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Author: tkelman

.travis.yml

@@ -68,7 +68,8 @@ before_install:
         ln -s /usr/bin/g++-5 $HOME/bin/x86_64-linux-gnu-g++;
         gcc --version;
         BAR="bar -i 30";
-        BUILDOPTS="-j3 VERBOSE=1 FORCE_ASSERTIONS=1 LLVM_ASSERTIONS=1";
+        BUILDOPTS="-j3 VERBOSE=1 FORCE_ASSERTIONS=1";
+# TODO: put LLVM_ASSERTIONS=1 back in BUILDOPTS, ref #19803
         echo "override ARCH=$ARCH" >> Make.user;
         TESTSTORUN="all";
       elif [ `uname` = "Darwin" ]; then