Fix Ruby environment

With “$(gem env gemdir)”, users reported that the gem was installed in
their home directory and not the default gem directory. This fixes that
by using the default gem installation directory instead.

.SRCINFO

@@ -1,7 +1,7 @@
 pkgbase = ruby-liquid
 	pkgdesc = Liquid markup language. Safe, customer facing template language for flexible web apps.
 	pkgver = 4.0.0
-	pkgrel = 1
+	pkgrel = 2
 	url = https://shopify.github.io/liquid/
 	arch = any
 	license = MIT
@@ -11,3 +11,4 @@ pkgbase = ruby-liquid
 	sha512sums = 3aa09813e2c6c3b75b9ab0eb1c11ae83f62e6d3dba19c91d8877bf8162edf867b06fbbc4fc3193116313ff98c1fa964b8a01f0cf58c9fb7ed89338f3bffb9cdb
 
 pkgname = ruby-liquid
+

PKGBUILD

@@ -3,7 +3,7 @@
 _gemname=liquid
 pkgname=ruby-$_gemname
 pkgver=4.0.0
-pkgrel=1
+pkgrel=2
 pkgdesc='Liquid markup language. Safe, customer facing template language for flexible web apps.'
 url='https://shopify.github.io/liquid/'
 arch=('any')
@@ -26,7 +26,7 @@ build() {
 
 package() {
   cd ${_gemname}-${pkgver}
-  local _gemdir="$(gem env gemdir)"
+  local _gemdir="$(ruby -e'puts Gem.default_dir')"
   gem install --ignore-dependencies --no-user-install -i "${pkgdir}${_gemdir}" -n "${pkgdir}/usr/bin" ${_gemname}-${pkgver}.gem
   install -Dm 644 README.md -t "${pkgdir}/usr/share/doc/${pkgname}"
   install -Dm 644 LICENSE -t "${pkgdir}/usr/share/licenses/${pkgname}"