gnumake/pkg-config toolchains are not reproducible

When evaluating the cache hit rates, we found a bunch of tools from rules_foreign_cc that are not reproducible and are causing cache misses.

The diff of execution log shows that, the same input produces different outputs:

```diff
spawn BootstrapPkgConfig @@rules_foreign_cc//toolchains/private:pkgconfig_tool_default differs, -spawn1 +spawn2:
&main.Spawn{
... // 3 identical fields
InputFiles: {&main.Directory{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Files: {&{Path: "bin/make", Digest: {Hash: "83a8c36b70875791558cc2da3121d47c57a162da6aaac47be52f996ff2b4f2cf", SizeBytes: 265288}}, &{Path: "include/gnumake.h", Digest: {Hash: "3e38df96688ba32938ece2070219684616bd157750c8ba5042ccb790a49dcacc", SizeBytes: 2913}}, &{Path: "share/info/make.info", Digest: {Hash: "f1c94cd2eaeacdd0825396e4f336701434380da93f8402b2eb64bd5249035a48", SizeBytes: 6518}}, &{Path: "share/info/make.info-1", Digest: {Hash: "50b1810947f3053d81dc1b5349369c31cc30c90d1bd8886f62ca9b360bbced55", SizeBytes: 301118}}, ...}}, &main.File{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Digest: {Hash: "fdd76db514ca7ce17ba131adf54e4ea4a65eb4bd9aef6b9f047887133d9f9000", SizeBytes: 2608}}, &main.File{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Digest: {Hash: "71ce8abeb9b324e04ccaf9505fbf15aab5d843f07c9c48824a256cf30cfad94e", SizeBytes: 1527}}, &main.File{Path: "external/llvm_toolchain/bin/cc_wrapper.sh", Digest: {Hash: "20d3e98de66875e5067fbc79003c4fb4e351b042da7e150e12e0556ebd84af48", SizeBytes: 6620}}, ...},
ToolFiles: {&main.Directory{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Files: {&{Path: "bin/make", Digest: {Hash: "83a8c36b70875791558cc2da3121d47c57a162da6aaac47be52f996ff2b4f2cf", SizeBytes: 265288}}, &{Path: "include/gnumake.h", Digest: {Hash: "3e38df96688ba32938ece2070219684616bd157750c8ba5042ccb790a49dcacc", SizeBytes: 2913}}, &{Path: "share/info/make.info", Digest: {Hash: "f1c94cd2eaeacdd0825396e4f336701434380da93f8402b2eb64bd5249035a48", SizeBytes: 6518}}, &{Path: "share/info/make.info-1", Digest: {Hash: "50b1810947f3053d81dc1b5349369c31cc30c90d1bd8886f62ca9b360bbced55", SizeBytes: 301118}}, ...}}, &main.File{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Digest: {Hash: "fdd76db514ca7ce17ba131adf54e4ea4a65eb4bd9aef6b9f047887133d9f9000", SizeBytes: 2608}}, &main.File{Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"..., Digest: {Hash: "71ce8abeb9b324e04ccaf9505fbf15aab5d843f07c9c48824a256cf30cfad94e", SizeBytes: 1527}}, &main.File{Path: "external/llvm_toolchain/bin/cc_wrapper.sh", Digest: {Hash: "20d3e98de66875e5067fbc79003c4fb4e351b042da7e150e12e0556ebd84af48", SizeBytes: 6620}}, ...},
Outputs: []main.FileLike{
&main.Directory{
Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"...,
Files: []*main.File{
&{
Path: "bin/arm-apple-darwin24.1.0-pkg-config",
Digest: main.Digest{
Hash: strings.Join({
- "fca472b0f36eee88bc5900e203780d179e5d18019bf904f0ad11ccc684e65942",
+ "6368a23ab04848a12caa9e770ffbcf9abb0fd5aef4a04208ea8ac3843fd7d2bb",
}, ""),
SizeBytes: 636392,
},
},
&{
Path: "bin/pkg-config",
Digest: main.Digest{
Hash: strings.Join({
- "fca472b0f36eee88bc5900e203780d179e5d18019bf904f0ad11ccc684e65942",
+ "6368a23ab04848a12caa9e770ffbcf9abb0fd5aef4a04208ea8ac3843fd7d2bb",
}, ""),
SizeBytes: 636392,
},
},
&{Path: "share/aclocal/pkg.m4", Digest: {Hash: "140b9a7bc1fa8730b62e74f8413af2bd15b53969a084fc4a041ba70b11e352f3", SizeBytes: 10247}},
&{Path: "share/doc/pkg-config/pkg-config-guide.html", Digest: {Hash: "abec943644a7c87d15bae2f5d5763488a592183ff35319732d44892a42a167c1", SizeBytes: 17832}},
&{Path: "share/man/man1/pkg-config.1", Digest: {Hash: "3591588e106c870d35f9da41bec0528a7e6577c45a97bb08766a33f1638a49f9", SizeBytes: 23611}},
},
},
&main.File{
Path: "bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rul"...,
Digest: main.Digest{
Hash: strings.Join({
- "4382c7005c073460b2c9032f6b5ce1de70d70b7686e3021473e959d1364422e",
+ "299b9fd99f6b847daaf3baa9de59d23f4b27f18ea01e9459d88222aea5193e5",
"a",
}, ""),
SizeBytes: 86548,
},
},
},
TargetLabel: "@@rules_foreign_cc//toolchains/private:pkgconfig_tool_default",
Mnemonic: "BootstrapPkgConfig",
... // 8 identical fields
}
```

After looking into the produced binaries, the diff is from the leaked sandbox path:

```shell
diff <(strings /Volumes/BazelCache/cache/cas/fc/fca472b0f36eee88bc5900e203780d179e5d18019bf904f0ad11ccc684e65942 | sort | uniq) <(strings /Volumes/BazelCache/cache/cas/63/6368a23ab04848a12caa9e770ffbcf9abb0fd5aef4a04208ea8ac3843fd7d2bb | sort | uniq)
230,231c230,231
< /private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/3217/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/lib
< /private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/3217/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/lib/pkgconfig:/private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/3217/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/share/pkgconfig
---
> /private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/4643/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/lib
> /private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/4643/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/lib/pkgconfig:/private/var/tmp/_bazel_xiaoyishi/79c76c5b4224312419386af2e6f9c092/sandbox/darwin-sandbox/4643/execroot/__main__/bazel-out/darwin_arm64-opt-exec-ST-a828a81199fe/bin/external/rules_foreign_cc/toolchains/private/pkgconfig/share/pkgconfig
```

No source files or tests are named. Start at the BootstrapPkgConfig action for @@rules_foreign_cc//toolchains/private:pkgconfig_tool_default and compare the generated binaries and execution logs shown in the issue. Done means repeated builds produce identical outputs without sandbox paths embedded in the binaries.

Written by the indexing model from the issue text.