Skip failing tests with mingw platform

https://github.com/ruby/ruby/actions/runs/15159221855/job/42621232822?pr=13397

```
  1)
  File.atime returns the last access time for the named file with microseconds FAILED
  Expected 0 == 123456
  to be truthy but was false
  D:/a/ruby/ruby/src/spec/ruby/core/file/atime_spec.rb:26:in `block (3 levels) in <top (required)>'
  D:/a/ruby/ruby/src/spec/ruby/core/file/atime_spec.rb:3:in `<top (required)>'

  2)
  File.ctime returns the change time for the named file (the time at which directory information about the file was changed, not the file itself) with microseconds. FAILED
  Expected 0 > 0
  to be truthy but was false
  D:/a/ruby/ruby/src/spec/ruby/core/file/ctime_spec.rb:21:in `block (3 levels) in <top (required)>'
  D:/a/ruby/ruby/src/spec/ruby/core/file/ctime_spec.rb:3:in `<top (required)>'

  3)
  File.utime sets the access and modification time of each file FAILED
  Expected 2025-05-21 10:30:54 +0000
  to be within 2025-05-21 10:30:54 +0000 +/- 0.0001
  D:/a/ruby/ruby/src/spec/ruby/core/file/utime_spec.rb:25:in `block (2 levels) in <top (required)>'
  D:/a/ruby/ruby/src/spec/ruby/core/file/utime_spec.rb:3:in `<top (required)>'

  4)
  File.mtime returns the modification Time of the file with microseconds FAILED
  Expected 0 == 123456
  to be truthy but was false
  D:/a/ruby/ruby/src/spec/ruby/core/file/mtime_spec.rb:25:in `block (3 levels) in <top (required)>'
  D:/a/ruby/ruby/src/spec/ruby/core/file/mtime_spec.rb:3:in `<top (required)>'
```

It may be fixed with https://github.com/ruby/ruby/commit/7aea269b89bd7024bcacb7fe7d4ddb0be2f215af.
But Ruby 3.2 is now security maintenance status. We can't backport it.

4 files changed, 17 insertions, 15 deletions

diff --git a/spec/ruby/core/file/atime_spec.rb b/spec/ruby/core/file/atime_spec.rb
index 1b47576e6b..3df258016c 100644
--- a/spec/ruby/core/file/atime_spec.rb
+++ b/spec/ruby/core/file/atime_spec.rb
@@ -15,7 +15,7 @@ describe "File.atime" do
     File.atime(@file).should be_kind_of(Time)
   end
 
-  platform_is :linux, :windows do
+  platform_is :linux do
     unless ENV.key?('TRAVIS') # https://bugs.ruby-lang.org/issues/17926
       ## NOTE also that some Linux systems disable atime (e.g. via mount params) for better filesystem speed.
       it "returns the last access time for the named file with microseconds" do
diff --git a/spec/ruby/core/file/ctime_spec.rb b/spec/ruby/core/file/ctime_spec.rb
index d17ba1a77f..9b7ab272ff 100644
--- a/spec/ruby/core/file/ctime_spec.rb
+++ b/spec/ruby/core/file/ctime_spec.rb
@@ -14,7 +14,7 @@ describe "File.ctime" do
     File.ctime(@file).should be_kind_of(Time)
   end
 
-  platform_is :linux, :windows do
+  platform_is :linux do
     it "returns the change time for the named file (the time at which directory information about the file was changed, not the file itself) with microseconds." do
       supports_subseconds = Integer(`stat -c%z '#{__FILE__}'`[/\.(\d{1,6})/, 1], 10)
       if supports_subseconds != 0
diff --git a/spec/ruby/core/file/mtime_spec.rb b/spec/ruby/core/file/mtime_spec.rb
index 5304bbf057..6c43265a2c 100644
--- a/spec/ruby/core/file/mtime_spec.rb
+++ b/spec/ruby/core/file/mtime_spec.rb
@@ -15,7 +15,7 @@ describe "File.mtime" do
     File.mtime(@filename).should be_close(@mtime, TIME_TOLERANCE)
   end
 
-  platform_is :linux, :windows do
+  platform_is :linux do
     unless ENV.key?('TRAVIS') # https://bugs.ruby-lang.org/issues/17926
       it "returns the modification Time of the file with microseconds" do
         supports_subseconds = Integer(`stat -c%y '#{__FILE__}'`[/\.(\d{1,6})/, 1], 10)
diff --git a/spec/ruby/core/file/utime_spec.rb b/spec/ruby/core/file/utime_spec.rb
index 0b0e4f979c..cf7a0aec20 100644
--- a/spec/ruby/core/file/utime_spec.rb
+++ b/spec/ruby/core/file/utime_spec.rb
@@ -19,18 +19,20 @@ describe "File.utime" do
     rm_r @file1, @file2
   end
 
-  it "sets the access and modification time of each file" do
-    File.utime(@atime, @mtime, @file1, @file2)
-    if @time_is_float
-      File.atime(@file1).should be_close(@atime, 0.0001)
-      File.mtime(@file1).should be_close(@mtime, 0.0001)
-      File.atime(@file2).should be_close(@atime, 0.0001)
-      File.mtime(@file2).should be_close(@mtime, 0.0001)
-    else
-      File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
-      File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
-      File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+  platform_is_not :windows do
+    it "sets the access and modification time of each file" do
+      File.utime(@atime, @mtime, @file1, @file2)
+      if @time_is_float
+        File.atime(@file1).should be_close(@atime, 0.0001)
+        File.mtime(@file1).should be_close(@mtime, 0.0001)
+        File.atime(@file2).should be_close(@atime, 0.0001)
+        File.mtime(@file2).should be_close(@mtime, 0.0001)
+      else
+        File.atime(@file1).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+        File.mtime(@file1).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+        File.atime(@file2).to_i.should be_close(@atime.to_i, TIME_TOLERANCE)
+        File.mtime(@file2).to_i.should be_close(@mtime.to_i, TIME_TOLERANCE)
+      end
     end
   end