patch required to build oracle plugin, collectd-5.4.0 (#653)

configure failed with Symbol 'OCIEnvCreate' not found.
$with_oracle_libs should be added in $LIBS, not in $LDFLAGS

config.log
```
configure:22597: checking for OCIEnvCreate
configure:22597: gcc -o conftest -g -O2  -I/app/oracle/product/11.2.0/xe/rdbms/public  -L/app/oracle/product/11.2.0/xe/lib -lclntsh conftest.c -ldl  >&5
/tmp/ccEel8Uy.o: In function `main':
/usr/local/src/collectd-5.4.0/conftest.c:214: undefined reference to `OCIEnvCreate'
collect2: error: ld returned 1 exit status
configure:22597: $? = 1
```

shouldn't this be SAVE_LIBS="$LIBS" ?