diff --git a/crates/tools/gnu/Cargo.toml b/crates/tools/gnu/Cargo.toml
index 037a495cba..a5a1c1720c 100644
--- a/crates/tools/gnu/Cargo.toml
+++ b/crates/tools/gnu/Cargo.toml
@@ -6,3 +6,4 @@ publish = false
 
 [dependencies]
 lib = { package = "tool_lib", path = "../lib" }
+which = "4"
diff --git a/crates/tools/gnu/readme.md b/crates/tools/gnu/readme.md
index f4a4d7b317..d8f9c3a60a 100644
--- a/crates/tools/gnu/readme.md
+++ b/crates/tools/gnu/readme.md
@@ -1,21 +1,8 @@
 The Windows umbrella lib (targeting GNU tooling) is generated using the following steps:
 
 0. Ensure MSYS2 MinGW environment is installed (https://www.mingw-w64.org/downloads/)
-1. Ensure `~\.cargo\config` has the following blocks to override toolchain defaults (customize paths as needed):
-
-    ```toml
-    [target.i686-pc-windows-gnu]
-    linker = "C:\\msys64\\mingw32\\bin\\i686-w64-mingw32-gcc.exe"
-    ar = "C:\\msys64\\mingw32\\bin\\ar.exe"
-
-    [target.x86_64-pc-windows-gnu]
-    linker = "C:\\msys64\\mingw64\\bin\\x86_64-w64-mingw32-gcc.exe"
-    ar = "C:\\msys64\\mingw64\\bin\\ar.exe"
-    ```
-
-1. Open `MSYS2 MinGW 32-bit`
+1. Open `MSYS2 MinGW 64-bit`
 2. Execute: `pacman -Syuu --noconfirm` (repeat until no further updates available)
 3. Repeat step 1 if needed
 4. Navigate to crate root
-5. Execute: `PATH=$USERPROFILE/.cargo/bin:$PATH cargo run -p tool_gnu --target i686-pc-windows-gnu`
-6. Repeat steps 1-5, using the `MSYS MinGW 64-bit` environment and `x86_64-pc-windows-gnu` target
+5. Execute: `PATH=$USERPROFILE/.cargo/bin:$PATH cargo run -p tool_gnu -- all`
diff --git a/crates/tools/gnu/src/main.rs b/crates/tools/gnu/src/main.rs
index 91b5c3a4ad..911ce86119 100644
--- a/crates/tools/gnu/src/main.rs
+++ b/crates/tools/gnu/src/main.rs
@@ -1,28 +1,37 @@
-use std::collections::BTreeMap;
+use std::collections::{BTreeMap, BTreeSet};
 use std::io::prelude::*;
 
 fn main() {
-    let mut cmd = std::process::Command::new("where");
-    cmd.arg("dlltool.exe");
-
-    let output = cmd.output().unwrap();
-
-    if !output.status.success() {
-        println!("dlltool.exe not found");
-        return;
+    for cmd in ["dlltool", "ar", "objcopy"] {
+        if which::which(cmd).is_err() {
+            eprintln!("Could not find {}. Is it in your $PATH?", cmd);
+            return;
+        }
+     }
+
+    const ALL_PLATFORMS: [&str; 2] = ["x86_64_gnu", "i686_gnu"];
+    let mut platforms = BTreeSet::new();
+    for platform in std::env::args().skip(1) {
+        if ALL_PLATFORMS.contains(&&*platform) {
+            platforms.insert(platform);
+        } else if platform == "all" {
+            platforms.extend(ALL_PLATFORMS.iter().map(|s| s.to_string()));
+        } else {
+            eprintln!("Unknown platform: {}", platform);
+            return;
+        }
     }
-
-    let output = unsafe { core::str::from_utf8_unchecked(&output.stdout) };
-
-    let platform = if output.contains("mingw64") {
-        "x86_64_gnu"
-    } else if output.contains("mingw32") {
-        "i686_gnu"
-    } else {
-        println!("mingw not found");
+    if platforms.is_empty() {
+        eprintln!("Please specify at least one platform or use 'all' argument");
         return;
     };
 
+    for platform in platforms {
+        build_platform(&platform);
+    }
+}
+
+fn build_platform(platform: &str) {
     println!("Platform: {}", platform);
 
     let libraries = lib::libraries();
@@ -81,6 +90,19 @@ EXPORTS
     cmd.arg(format!("{}.def", library));
     cmd.arg("-l");
     cmd.arg(format!("lib{}.a", library));
+    cmd.arg("-m");
+    cmd.arg(match platform {
+        "i686_gnu" => "i386",
+        "x86_64_gnu" => "i386:x86-64",
+        _ => unreachable!(),
+    });
+    // Work around https://sourceware.org/bugzilla/show_bug.cgi?id=29497
+    cmd.arg("-f");
+    cmd.arg(match platform {
+        "i686_gnu" => "--32",
+        "x86_64_gnu" => "--64",
+        _ => unreachable!(),
+    });
     // Ensure consistency in the prefixes used by dlltool.
     cmd.arg("-t");
     if library.contains('.') {