[Github][libc] Hash Pin Actions in Workflows (#129487)

This patch has pins actions in the libc Github workflows. Hash pinning
is a best practice as it ensures we are getting an exact action version,
which can help with reproducibility/reliability. It additionally
alleviates security concerns as an attacker can modify release assets,
potentially giving them access to tokens in privileged workflows.

.github/workflows/libc-fullbuild-tests.yml

@@ -30,7 +30,7 @@ jobs:
           # - c_compiler: gcc
           #   cpp_compiler: g++
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     
     # Libc's build is relatively small comparing with other components of LLVM.
     # A fresh fullbuild takes about 190MiB of uncompressed disk space, which can
@@ -39,7 +39,7 @@ jobs:
     # Do not use direct GHAC access even though it is supported by sccache. GHAC rejects
     # frequent small object writes.
     - name: Setup ccache
-      uses: hendrikmuhs/ccache-action@v1.2
+      uses: hendrikmuhs/ccache-action@a1209f81afb8c005c13b4296c32e363431bffea5 # v1.2.17
       with:
         max-size: 1G
         key: libc_fullbuild_${{ matrix.c_compiler }}

.github/workflows/libc-overlay-tests.yml

@@ -47,7 +47,7 @@ jobs:
               cpp_compiler: clang++
     
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
     
     # Libc's build is relatively small comparing with other components of LLVM.
     # A fresh linux overlay takes about 180MiB of uncompressed disk space, which can
@@ -57,7 +57,7 @@ jobs:
     # Do not use direct GHAC access even though it is supported by sccache. GHAC rejects
     # frequent small object writes.
     - name: Setup ccache
-      uses: hendrikmuhs/ccache-action@v1
+      uses: hendrikmuhs/ccache-action@a1209f81afb8c005c13b4296c32e363431bffea5 # v1.2.17
       with:
         max-size: 1G
         key: libc_overlay_build_${{ matrix.os }}_${{ matrix.compiler.c_compiler }}