[libc][math] Enable math acos for baremetal Arm and AArch64 (#166749)

This patch adds `acos` to the entrypoints of baremetal Arm and AArch64.

Tests have been run with Arm Toolchain for Embedded, a downstream
toolchain, in conjunction with qemu, across several configurations of
FPUs and architecture versions. All tests run are passing.
diff --git a/libc/config/baremetal/aarch64/entrypoints.txt b/libc/config/baremetal/aarch64/entrypoints.txt
index ab0ac7c..049adb34 100644
--- a/libc/config/baremetal/aarch64/entrypoints.txt
+++ b/libc/config/baremetal/aarch64/entrypoints.txt
@@ -320,6 +320,7 @@
     libc.src.fenv.feupdateenv
 
     # math.h entrypoints
+    libc.src.math.acos
     libc.src.math.acosf
     libc.src.math.acoshf
     libc.src.math.asinf
diff --git a/libc/config/baremetal/arm/entrypoints.txt b/libc/config/baremetal/arm/entrypoints.txt
index 96afb88..2444ec5 100644
--- a/libc/config/baremetal/arm/entrypoints.txt
+++ b/libc/config/baremetal/arm/entrypoints.txt
@@ -323,6 +323,7 @@
     libc.src.fenv.feupdateenv
 
     # math.h entrypoints
+    libc.src.math.acos
     libc.src.math.acosf
     libc.src.math.acoshf
     libc.src.math.asinf