Revert "Bump target minimum macOS version from 10.13.0 to 10.13.4"

This reverts commit 4c7b4a5.

Author: zanieb

cpython-unix/targets.yml

@@ -566,7 +566,7 @@ x86_64-apple-darwin:
   target_cflags:
     - '-arch'
     - 'x86_64'
-    - '-mmacosx-version-min=10.13.4'
+    - '-mmacosx-version-min=10.13'
     # Suppress extremely verbose warnings we see with LLVM 10.
     - '-Wno-nullability-completeness'
     - '-Wno-expansion-to-defined'
@@ -581,7 +581,7 @@ x86_64-apple-darwin:
   target_ldflags:
     - '-arch'
     - 'x86_64'
-    - '-mmacosx-version-min=10.13.4'
+    - '-mmacosx-version-min=10.13'
   needs:
     - autoconf
     - bzip2

src/validation.rs

@@ -1100,7 +1100,7 @@ fn validate_macho<Mach: MachHeader<Endian = Endianness>>(
     bytes: &[u8],
 ) -> Result<()> {
     let advertised_target_version =
-        semver::Version::parse(&format!("{}", advertised_target_version))?;
+        semver::Version::parse(&format!("{}.0", advertised_target_version))?;
     let advertised_sdk_version = semver::Version::parse(&format!("{}.0", advertised_sdk_version))?;
 
     let endian = header.endian()?;