scripts: fix overextending of variable name (#4888)

scripts/build_freebsd.sh

@@ -1,6 +1,6 @@
 outPlattform=freebsd
 outArch=amd64
-outPath=./output_$outPlattform_$outArch
+outPath=./output_${outPlattform}_$outArch
 
 rm -rf $outPath
 mkdir $outPath

scripts/build_linux64.sh

@@ -1,6 +1,6 @@
 outPlattform=linux
 outArch=amd64
-outPath=./output_$outPlattform_$outArch
+outPath=./output_${outPlattform}_$outArch
 
 rm -rf $outPath
 mkdir $outPath