Fixed two typos in c2f0673

I made two stupid mistakes when copying and pasting the changes to
scripts that had more than one existing argument. Good thing I
double-checked the diff on GitHub.

Author: etremel

scripts/prerequisites/install-libtorch.sh

@@ -6,7 +6,7 @@ if [ $# -lt 1 ]; then
 fi
 
 INSTALL_PREFIX="/usr/local"
-if [[ $# -gt 0 ]]; then
+if [[ $# -gt 1 ]]; then
     INSTALL_PREFIX=$2
 fi
 INSTALL_TYPE=$1

scripts/prerequisites/install-tensorflow.sh

@@ -7,7 +7,7 @@ fi
 
 # pip3 install tensorflow==${VERSION}
 INSTALL_PREFIX="/usr/local"
-if [[ $# -gt 0 ]]; then
+if [[ $# -gt 2 ]]; then
     INSTALL_PREFIX=$3
 fi
 VERSION=$1