[CI][Dev] Fix shellcheck errors in the ci/scripts/r_docker_configure.sh #50766

shellcheck ci/scripts/r_docker_configure.sh

In ci/scripts/r_docker_configure.sh line 21:
: ${R_BIN:=R}
  ^---------^ SC2223 (info): This default assignment may cause DoS due to globbing. Quote it.


In ci/scripts/r_docker_configure.sh line 23:
: ${ARROW_SOURCE_HOME:=/arrow}
  ^--------------------------^ SC2223 (info): This default assignment may cause DoS due to globbing. Quote it.


In ci/scripts/r_docker_configure.sh line 29:
  cat ${ARROW_SOURCE_HOME}/ci/etc/rprofile >> $(${R_BIN} RHOME)/etc/Rprofile.site
      ^------------------^ SC2086 (info): Double quote to prevent globbing and word splitting.
                                              ^---------------^ SC2046 (warning): Quote this to prevent word splitting.

Did you mean:
  cat "${ARROW_SOURCE_HOME}"/ci/etc/rprofile >> $(${R_BIN} RHOME)/etc/Rprofile.site


In ci/scripts/r_docker_configure.sh line 33:
echo "MAKEFLAGS=-j$(${R_BIN} -s -e 'cat(parallel::detectCores())')" >> $(R RHOME)/etc/Renviron.site
                                                                       ^--------^ SC2046 (warning): Quote this to prevent word splitting.


In ci/scripts/r_docker_configure.sh line 36:
if [ "`which dnf`" ]; then
      ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.

Did you mean:
if [ "$(which dnf)" ]; then


In ci/scripts/r_docker_configure.sh line 38:
elif [ "`which yum`" ]; then
        ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.

Did you mean:
elif [ "$(which yum)" ]; then


In ci/scripts/r_docker_configure.sh line 40:
elif [ "`which zypper`" ]; then
        ^------------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.

Did you mean:
elif [ "$(which zypper)" ]; then


In ci/scripts/r_docker_configure.sh line 42:
elif [ "`which apk`" ]; then
        ^---------^ SC2006 (style): Use $(...) notation instead of legacy backticks `...`.

Did you mean:
elif [ "$(which apk)" ]; then


In ci/scripts/r_docker_configure.sh line 50:
: ${R_CUSTOM_CCACHE:=FALSE}
  ^-----------------------^ SC2223 (info): This default assignment may cause DoS due to globbing. Quote it.


In ci/scripts/r_docker_configure.sh line 51:
R_CUSTOM_CCACHE=`echo $R_CUSTOM_CCACHE | tr '[:upper:]' '[:lower:]'`
                ^-- SC2006 (style): Use $(...) notation instead of legacy backticks `...`.
                      ^--------------^ SC2086 (info): Double quote to prevent globbing and word splitting.

Did you mean:
R_CUSTOM_CCACHE=$(echo "$R_CUSTOM_CCACHE" | tr '[:upper:]' '[:lower:]')


In ci/scripts/r_docker_configure.sh line 52:
if [ ${R_CUSTOM_CCACHE} = "true" ]; then
     ^----------------^ SC2086 (info): Double quote to prevent globbing and word splitting.

Did you mean:
if [ "${R_CUSTOM_CCACHE}" = "true" ]; then

For more information:
  https://www.shellcheck.net/wiki/SC2046 -- Quote this to prevent word splitt...
  https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
  https://www.shellcheck.net/wiki/SC2223 -- This default assignment may cause...