Remove explicit set of `DISABLE_GEMS`

`DISABLE_GEMS` is automatically set (or unset); ref #790

build_config.rb

@@ -29,7 +29,7 @@ MRuby::Build.new do |conf|
   #   cc.command = ENV['CC'] || 'gcc'
   #   cc.flags = [ENV['CFLAGS'] || %w()]
   #   cc.include_paths = ["#{root}/include"]
-  #   cc.defines = %w(DISABLE_GEMS)
+  #   cc.defines = %w()
   #   cc.option_include_path = '-I%s'
   #   cc.option_define = '-D%s'
   #   cc.compile_options = "%{flags} -MMD -o %{outfile} -c %{infile}"

tasks/toolchains/gcc.rake

@@ -2,7 +2,6 @@ MRuby::Toolchain.new(:gcc) do |conf, _params|
   [conf.cc, conf.objc, conf.asm].each do |cc|
     cc.command = ENV['CC'] || 'gcc'
     cc.flags = [ENV['CFLAGS'] || %w(-g -std=gnu99 -O3 -Wall -Werror-implicit-function-declaration -Wdeclaration-after-statement -Wwrite-strings -Wundef)]
-    cc.defines = %w(DISABLE_GEMS)
     cc.option_include_path = '-I%s'
     cc.option_define = '-D%s'
     cc.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'
@@ -13,7 +12,6 @@ MRuby::Toolchain.new(:gcc) do |conf, _params|
   [conf.cxx].each do |cxx|
     cxx.command = ENV['CXX'] || 'g++'
     cxx.flags = [ENV['CXXFLAGS'] || ENV['CFLAGS'] || %w(-g -O3 -Wall -Werror-implicit-function-declaration -Wundef)]
-    cxx.defines = %w(DISABLE_GEMS)
     cxx.option_include_path = '-I%s'
     cxx.option_define = '-D%s'
     cxx.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'

tasks/toolchains/openwrt.rake

@@ -5,7 +5,6 @@ MRuby::Toolchain.new(:openwrt) do |conf|
     cc.command = ENV['TARGET_CC']
     cc.flags = ENV['TARGET_CFLAGS']
     cc.include_paths = ["#{MRUBY_ROOT}/include"]
-    cc.defines = %w(DISABLE_GEMS)
     cc.option_include_path = '-I%s'
     cc.option_define = '-D%s'
     cc.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'
@@ -15,7 +14,6 @@ MRuby::Toolchain.new(:openwrt) do |conf|
     cxx.command = ENV['TARGET_CXX']
     cxx.flags = ENV['TARGET_CXXFLAGS']
     cxx.include_paths = ["#{MRUBY_ROOT}/include"]
-    cxx.defines = %w(DISABLE_GEMS)
     cxx.option_include_path = '-I%s'
     cxx.option_define = '-D%s'
     cxx.compile_options = '%{flags} -MMD -o %{outfile} -c %{infile}'

tasks/toolchains/visualcpp.rake

@@ -3,7 +3,7 @@ MRuby::Toolchain.new(:visualcpp) do |conf, _params|
     cc.command = ENV['CC'] || 'cl.exe'
     # C4013: implicit function declaration
     cc.flags = [ENV['CFLAGS'] || %w(/c /nologo /W3 /we4013 /Zi /MD /O2 /D_CRT_SECURE_NO_WARNINGS)]
-    cc.defines = %w(DISABLE_GEMS MRB_STACK_EXTEND_DOUBLING)
+    cc.defines = %w(MRB_STACK_EXTEND_DOUBLING)
     cc.option_include_path = '/I%s'
     cc.option_define = '/D%s'
     cc.compile_options = "%{flags} /Fo%{outfile} %{infile}"
@@ -14,7 +14,7 @@ MRuby::Toolchain.new(:visualcpp) do |conf, _params|
   conf.cxx do |cxx|
     cxx.command = ENV['CXX'] || 'cl.exe'
     cxx.flags = [ENV['CXXFLAGS'] || ENV['CFLAGS'] || %w(/c /nologo /W3 /Zi /MD /O2 /EHs /D_CRT_SECURE_NO_WARNINGS)]
-    cxx.defines = %w(DISABLE_GEMS MRB_STACK_EXTEND_DOUBLING)
+    cxx.defines = %w(MRB_STACK_EXTEND_DOUBLING)
     cxx.option_include_path = '/I%s'
     cxx.option_define = '/D%s'
     cxx.compile_options = "%{flags} /Fo%{outfile} %{infile}"