diff --git a/llvm/test/tools/llvm-elfabi/fail-file-write-windows.test b/llvm/test/tools/llvm-elfabi/fail-file-write-windows.test
--- a/llvm/test/tools/llvm-elfabi/fail-file-write-windows.test
+++ b/llvm/test/tools/llvm-elfabi/fail-file-write-windows.test
@@ -3,7 +3,7 @@
 # REQUIRES: system-windows
 # RUN: touch %t.TestFile
 # RUN: chmod 400 %t.TestFile
-# RUN: not llvm-elfabi %s --output-target=elf64-little %t.TestFile 2>&1 | FileCheck %s --check-prefix=ERR
+# RUN: not llvm-elfabi %s --output-target=elf64-little %t.TestFile 2>&1 | FileCheck -DMSG=%errc_EACCES %s --check-prefix=ERR
 # RUN: chmod 777 %t.TestFile
 # RUN: rm -rf %t.TestFile
 
@@ -13,4 +13,4 @@
 Symbols: {}
 ...
 
-# ERR: error: permission denied
+# ERR: error: [[MSG]]
diff --git a/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubnames.yaml b/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubnames.yaml
--- a/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubnames.yaml
+++ b/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubnames.yaml
@@ -225,7 +225,7 @@
 
 ## h) Test that yaml2obj emits an error if 'Descriptor' is missing.
 
-# RUN: not yaml2obj --docnum=8 %s -o %t8.o 2>&1 | FileCheck -DMSG=%errc_EINVAL %s --check-prefix=MISSING-KEY --ignore-case
+# RUN: not yaml2obj --docnum=8 %s -o %t8.o 2>&1 | FileCheck -DMSG=%errc_EINVAL %s --check-prefix=MISSING-KEY
 
 #      MISSING-KEY: YAML:{{.*}}:9: error: missing required key 'Descriptor'
 # MISSING-KEY-NEXT:       - DieOffset: 0x12345678
diff --git a/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubtypes.yaml b/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubtypes.yaml
--- a/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubtypes.yaml
+++ b/llvm/test/tools/yaml2obj/ELF/DWARF/debug-gnu-pubtypes.yaml
@@ -225,12 +225,12 @@
 
 ## h) Test that yaml2obj emits an error if 'Descriptor' is missing.
 
-# RUN: not yaml2obj --docnum=8 %s -o %t8.o 2>&1 | FileCheck %s --check-prefix=MISSING-KEY --ignore-case
+# RUN: not yaml2obj --docnum=8 %s -o %t8.o 2>&1 | FileCheck -DMSG=%errc_EINVAL %s --check-prefix=MISSING-KEY
 
 #      MISSING-KEY: YAML:{{.*}}:9: error: missing required key 'Descriptor'
 # MISSING-KEY-NEXT:       - DieOffset: 0x12345678
 # MISSING-KEY-NEXT:         ^
-# MISSING-KEY-NEXT: yaml2obj: error: failed to parse YAML input: Invalid argument
+# MISSING-KEY-NEXT: yaml2obj: error: failed to parse YAML input: [[MSG]]
 
 --- !ELF
 FileHeader:
diff --git a/llvm/utils/lit/lit/llvm/config.py b/llvm/utils/lit/lit/llvm/config.py
--- a/llvm/utils/lit/lit/llvm/config.py
+++ b/llvm/utils/lit/lit/llvm/config.py
@@ -4,6 +4,7 @@
 import re
 import subprocess
 import sys
+import errno
 
 import lit.util
 from lit.llvm.subst import FindTool
@@ -346,21 +347,19 @@
         return True
 
     def add_err_msg_substitutions(self):
-        if (sys.platform == 'zos'):
-            self.config.substitutions.append(('%errc_ENOENT', '\'EDC5129I No such file or directory.\''))
-            self.config.substitutions.append(('%errc_EISDIR', '\'EDC5123I Is a directory.\''))
-            self.config.substitutions.append(('%errc_EINVAL', '\'EDC5121I Invalid argument.\''))
-            self.config.substitutions.append(('%errc_EACCES', '\'EDC5111I Permission denied.\''))
-        elif (sys.platform == 'win32'):
+        host_cxx = getattr(self.config, 'host_cxx', '')
+        # On Windows, python's os.strerror() does not emit the same spelling as the C++ std::error_code.
+        # As a workaround, hardcode the Windows error message.
+        if (sys.platform == 'win32' and 'MSYS' not in host_cxx):
             self.config.substitutions.append(('%errc_ENOENT', '\'no such file or directory\''))
             self.config.substitutions.append(('%errc_EISDIR', '\'is a directory\''))
             self.config.substitutions.append(('%errc_EINVAL', '\'invalid argument\''))
             self.config.substitutions.append(('%errc_EACCES', '\'permission denied\''))
         else:
-            self.config.substitutions.append(('%errc_ENOENT', '\'No such file or directory\''))
-            self.config.substitutions.append(('%errc_EISDIR', '\'Is a directory\''))
-            self.config.substitutions.append(('%errc_EINVAL', '\'Invalid argument\''))
-            self.config.substitutions.append(('%errc_EACCES', '\'Permission denied\''))
+            self.config.substitutions.append(('%errc_ENOENT', '\'' + os.strerror(errno.ENOENT) + '\''))
+            self.config.substitutions.append(('%errc_EISDIR', '\'' + os.strerror(errno.EISDIR) + '\''))
+            self.config.substitutions.append(('%errc_EINVAL', '\'' + os.strerror(errno.EINVAL) + '\''))
+            self.config.substitutions.append(('%errc_EACCES', '\'' + os.strerror(errno.EACCES) + '\''))
 
     def use_default_substitutions(self):
         tool_patterns = [